diff --git a/projects/ad9265_fmc/zc706/system_top.v b/projects/ad9265_fmc/zc706/system_top.v
index 0933e5b8e..2b9bb5938 100644
--- a/projects/ad9265_fmc/zc706/system_top.v
+++ b/projects/ad9265_fmc/zc706/system_top.v
@@ -113,7 +113,7 @@ ad_iobuf #(.DATA_WIDTH(15)) iobuf_gpio_bd (
   .dio_t (gpio_t[14:0]),
   .dio_p (gpio_bd));
 
-assign gpio_i[63:15] = gpio_o[63:15];
+assign gpio_i[63:15] = 'h0;
 
 ad9265_spi i_spi (
     .spi_csn(spi0_csn[1:0]),
diff --git a/projects/ad9434_fmc/zc706/system_top.v b/projects/ad9434_fmc/zc706/system_top.v
index 3bcf4b5b9..53ab0ef0d 100644
--- a/projects/ad9434_fmc/zc706/system_top.v
+++ b/projects/ad9434_fmc/zc706/system_top.v
@@ -99,7 +99,7 @@ module system_top (
 
   // assignments
 
-  assign gpio_i[63:15] = gpio_o[63:15];
+  assign gpio_i[63:15] = 'h0;
 
   // instantiations
 
diff --git a/projects/ad9467_fmc/kc705/system_top.v b/projects/ad9467_fmc/kc705/system_top.v
index 8c92b694d..4ffeb2acc 100644
--- a/projects/ad9467_fmc/kc705/system_top.v
+++ b/projects/ad9467_fmc/kc705/system_top.v
@@ -133,8 +133,8 @@ module system_top (
      .dio_o (gpio_i[16:0]),
      .dio_p (gpio_bd));
 
-  assign gpio_i[63:32] = gpio_o[63:32];
-  assign gpio_i[31:17] = gpio_o[31:17];
+  assign gpio_i[63:32] = 'h0;
+  assign gpio_i[31:17] = 'h0;
 
   system_wrapper i_system_wrapper (
       .ddr3_addr (ddr3_addr),
diff --git a/projects/ad9467_fmc/zed/system_top.v b/projects/ad9467_fmc/zed/system_top.v
index 04a5dd2c2..490c66dc4 100644
--- a/projects/ad9467_fmc/zed/system_top.v
+++ b/projects/ad9467_fmc/zed/system_top.v
@@ -115,7 +115,7 @@ wire            iic_mux_sda_t_s;
     .dio_o ({gpio_i[31:0]}),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:32] = gpio_o[63:32];
+  assign gpio_i[63:32] = 'h0;
 
    ad_iobuf #(.DATA_WIDTH(2)) i_iobuf_iic_scl (
     .dio_t ({iic_mux_scl_t_s,iic_mux_scl_t_s}),
diff --git a/projects/ad9739a_fmc/zc706/system_top.v b/projects/ad9739a_fmc/zc706/system_top.v
index 505c60a37..c100b5279 100644
--- a/projects/ad9739a_fmc/zc706/system_top.v
+++ b/projects/ad9739a_fmc/zc706/system_top.v
@@ -118,7 +118,7 @@ module system_top (
     .dio_o (gpio_i[14:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:15] = gpio_o[63:15];
+  assign gpio_i[63:15] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr_addr (ddr_addr),
diff --git a/projects/adrv9009/zcu102/system_top.v b/projects/adrv9009/zcu102/system_top.v
index 53830bb05..584fe2abd 100644
--- a/projects/adrv9009/zcu102/system_top.v
+++ b/projects/adrv9009/zcu102/system_top.v
@@ -115,8 +115,8 @@ module system_top (
   wire                    tx_sync;
   wire                    sysref;
 
-  assign gpio_i[94:60] = gpio_o[94:60];
-  assign gpio_i[31:21] = gpio_o[31:21];
+  assign gpio_i[94:60] = 'h0;
+  assign gpio_i[31:21] = 'h0;
 
   assign sysref_out = 0;
 
@@ -199,7 +199,7 @@ module system_top (
               adrv9009_gpio_16,     // 33
               adrv9009_gpio_18}));  // 32
 
-  assign gpio_i[ 7: 0] = gpio_o[ 7: 0];
+  assign gpio_i[ 7: 0] = 'h0;
   assign gpio_i[20: 8] = gpio_bd_i;
   assign gpio_bd_o = gpio_o[ 7: 0];
 
diff --git a/projects/adrv9361z7035/ccbob_cmos/system_top.v b/projects/adrv9361z7035/ccbob_cmos/system_top.v
index d82381da0..d1efd7813 100644
--- a/projects/adrv9361z7035/ccbob_cmos/system_top.v
+++ b/projects/adrv9361z7035/ccbob_cmos/system_top.v
@@ -128,7 +128,7 @@ module system_top (
 
   // board gpio - 31-0
 
-  assign gpio_i[31:20] = gpio_o[31:20];
+  assign gpio_i[31:20] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(20)) i_iobuf_bd (
     .dio_t (gpio_t[19:0]),
@@ -138,8 +138,8 @@ module system_top (
 
   // ad9361 gpio - 63-32
 
-  assign gpio_i[63:52] = gpio_o[63:52];
-  assign gpio_i[50:47] = gpio_o[50:47];
+  assign gpio_i[63:52] = 'h0;
+  assign gpio_i[50:47] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(16)) i_iobuf (
     .dio_t ({gpio_t[51], gpio_t[46:32]}),
diff --git a/projects/adrv9361z7035/ccbob_lvds/system_top.v b/projects/adrv9361z7035/ccbob_lvds/system_top.v
index b2434a4d9..169dc3c8b 100644
--- a/projects/adrv9361z7035/ccbob_lvds/system_top.v
+++ b/projects/adrv9361z7035/ccbob_lvds/system_top.v
@@ -132,7 +132,7 @@ module system_top (
 
   // board gpio - 31-0
 
-  assign gpio_i[31:20] = gpio_o[31:20];
+  assign gpio_i[31:20] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(20)) i_iobuf_bd (
     .dio_t (gpio_t[19:0]),
@@ -142,8 +142,8 @@ module system_top (
 
   // ad9361 gpio - 63-32
 
-  assign gpio_i[63:52] = gpio_o[63:52];
-  assign gpio_i[50:47] = gpio_o[50:47];
+  assign gpio_i[63:52] = 'h0;
+  assign gpio_i[50:47] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(16)) i_iobuf (
     .dio_t ({gpio_t[51], gpio_t[46:32]}),
diff --git a/projects/adrv9361z7035/ccbox_lvds/system_top.v b/projects/adrv9361z7035/ccbox_lvds/system_top.v
index f00b46c2b..c1b9b9a0b 100644
--- a/projects/adrv9361z7035/ccbox_lvds/system_top.v
+++ b/projects/adrv9361z7035/ccbox_lvds/system_top.v
@@ -159,9 +159,9 @@ module system_top (
 
   // gpio[31:20] controls misc stuff (keep as io)
 
-  assign gpio_i[31:29] = gpio_o[31:29];
+  assign gpio_i[31:29] = 'h0;
   assign gpio_i[28:28] = imu_ready;
-  assign gpio_i[27:27] = gpio_o[27:27];
+  assign gpio_i[27:27] = 'h0;
 
   // rtc int gpio - 26
 
@@ -193,7 +193,7 @@ module system_top (
 
   // gpio[19:16] controls adp5061 (keep as io)
 
-  assign gpio_i[19] = gpio_o[19];
+  assign gpio_i[19] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(3)) i_iobuf_adp5061 (
     .dio_t (gpio_t[18:16]),
@@ -210,7 +210,7 @@ module system_top (
   assign oled_dc = gpio_o[11];
   assign oled_rst = gpio_o[10];
   assign imu_rstn = gpio_o[9];
-  assign gpio_i[11:9] = gpio_o[11:9];
+  assign gpio_i[11:9] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(1)) i_iobuf_imu_sync (
     .dio_t (gpio_t[8]),
@@ -230,14 +230,14 @@ module system_top (
   assign switch_led_r = gpio_o[2];
   assign switch_led_g = gpio_o[1];
   assign switch_led_b = gpio_o[0];
-  assign gpio_i[3:0] = gpio_o[3:0];
+  assign gpio_i[3:0] = 'h0;
 
   // unused gpio - 63:30
 
-  assign gpio_i[63] = gpio_o[63];
-  assign gpio_i[62] = gpio_o[62];
-  assign gpio_i[61] = gpio_o[61];
-  assign gpio_i[60] = gpio_o[60];
+  assign gpio_i[63] = 'h0;
+  assign gpio_i[62] = 'h0;
+  assign gpio_i[61] = 'h0;
+  assign gpio_i[60] = 'h0;
 
   // tsw-part-2 gpio - 59:57
 
@@ -259,7 +259,7 @@ module system_top (
 
   // unused gpio - 55:53
 
-  assign gpio_i[55:53] = gpio_o[55:53];
+  assign gpio_i[55:53] = 'h0;
 
   // rf & clock-select gpio - 52:51
 
diff --git a/projects/adrv9361z7035/ccfmc_lvds/system_top.v b/projects/adrv9361z7035/ccfmc_lvds/system_top.v
index b1d2ab64b..6fbfb6ded 100644
--- a/projects/adrv9361z7035/ccfmc_lvds/system_top.v
+++ b/projects/adrv9361z7035/ccfmc_lvds/system_top.v
@@ -227,7 +227,7 @@ module system_top (
 
   // board gpio - 31-0
 
-  assign gpio_i[31:21] = gpio_o[31:21];
+  assign gpio_i[31:21] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(21)) i_iobuf_bd (
     .dio_t (gpio_t[20:0]),
@@ -237,7 +237,7 @@ module system_top (
 
   // unused gpio - 63-61
 
-  assign gpio_i[63:61] = gpio_o[63:61];
+  assign gpio_i[63:61] = 'h0;
 
   // rf & ad9517 gpio - 60:56
 
@@ -253,7 +253,7 @@ module system_top (
 
   // unused gpio - 55:53
 
-  assign gpio_i[55:53] = gpio_o[55:53];
+  assign gpio_i[55:53] = 'h0;
 
   // rf & clock-select gpio - 52:51
 
@@ -266,7 +266,7 @@ module system_top (
 
   // unused gpio - 50:47
 
-  assign gpio_i[50:47] = gpio_o[50:47];
+  assign gpio_i[50:47] = 'h0;
 
   // ad9361 gpio - 46:32
 
diff --git a/projects/adrv9364z7020/ccbob_cmos/system_top.v b/projects/adrv9364z7020/ccbob_cmos/system_top.v
index fd587de0d..f41b80998 100644
--- a/projects/adrv9364z7020/ccbob_cmos/system_top.v
+++ b/projects/adrv9364z7020/ccbob_cmos/system_top.v
@@ -112,7 +112,7 @@ module system_top (
 
   // board gpio - 31-0
 
-  assign gpio_i[31:11] = gpio_o[31:11];
+  assign gpio_i[31:11] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(11)) i_iobuf_bd (
     .dio_t (gpio_t[10:0]),
@@ -122,8 +122,8 @@ module system_top (
 
   // ad9361 gpio - 63-32
 
-  assign gpio_i[63:52] = gpio_o[63:52];
-  assign gpio_i[50:47] = gpio_o[50:47];
+  assign gpio_i[63:52] = 'h0;
+  assign gpio_i[50:47] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(16)) i_iobuf (
     .dio_t ({gpio_t[51], gpio_t[46:32]}),
diff --git a/projects/adrv9364z7020/ccbob_lvds/system_top.v b/projects/adrv9364z7020/ccbob_lvds/system_top.v
index 2cb88227a..25145ee58 100644
--- a/projects/adrv9364z7020/ccbob_lvds/system_top.v
+++ b/projects/adrv9364z7020/ccbob_lvds/system_top.v
@@ -116,7 +116,7 @@ module system_top (
 
   // board gpio - 31-0
 
-  assign gpio_i[31:11] = gpio_o[31:11];
+  assign gpio_i[31:11] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(11)) i_iobuf_bd (
     .dio_t (gpio_t[10:0]),
@@ -126,8 +126,8 @@ module system_top (
 
   // ad9361 gpio - 63-32
 
-  assign gpio_i[63:52] = gpio_o[63:52];
-  assign gpio_i[50:47] = gpio_o[50:47];
+  assign gpio_i[63:52] = 'h0;
+  assign gpio_i[50:47] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(16)) i_iobuf (
     .dio_t ({gpio_t[51], gpio_t[46:32]}),
diff --git a/projects/adrv9364z7020/ccbox_lvds/system_top.v b/projects/adrv9364z7020/ccbox_lvds/system_top.v
index 908a9290d..e046ebe2e 100644
--- a/projects/adrv9364z7020/ccbox_lvds/system_top.v
+++ b/projects/adrv9364z7020/ccbox_lvds/system_top.v
@@ -157,9 +157,9 @@ module system_top (
 
   // gpio[31:20] controls misc stuff (keep as io)
 
-  assign gpio_i[31:29] = gpio_o[31:29];
+  assign gpio_i[31:29] = 'h0;
   assign gpio_i[28:28] = imu_ready;
-  assign gpio_i[27:27] = gpio_o[27:27];
+  assign gpio_i[27:27] = 'h0;
 
   // rtc int gpio - 26
 
@@ -171,7 +171,7 @@ module system_top (
 
   // unused gpio - 25:24
 
-  assign gpio_i[25:24] = gpio_o[25:24];
+  assign gpio_i[25:24] = 'h0;
 
   // misc gpio - 23:20
 
@@ -186,7 +186,7 @@ module system_top (
 
   // gpio[19:16] controls adp5061 (keep as io)
 
-  assign gpio_i[19] = gpio_o[19];
+  assign gpio_i[19] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(3)) i_iobuf_adp5061 (
     .dio_t (gpio_t[18:16]),
@@ -203,7 +203,7 @@ module system_top (
   assign oled_dc = gpio_o[11];
   assign oled_rst = gpio_o[10];
   assign imu_rstn = gpio_o[9];
-  assign gpio_i[11:9] = gpio_o[11:9];
+  assign gpio_i[11:9] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(1)) i_iobuf_imu_sync (
     .dio_t (gpio_t[8]),
@@ -223,14 +223,14 @@ module system_top (
   assign switch_led_r = gpio_o[2];
   assign switch_led_g = gpio_o[1];
   assign switch_led_b = gpio_o[0];
-  assign gpio_i[3:0] = gpio_o[3:0];
+  assign gpio_i[3:0] = 'h0;
 
   // unused gpio - 63:30
 
-  assign gpio_i[63] = gpio_o[63];
-  assign gpio_i[62] = gpio_o[62];
-  assign gpio_i[61] = gpio_o[61];
-  assign gpio_i[60] = gpio_o[60];
+  assign gpio_i[63] = 'h0;
+  assign gpio_i[62] = 'h0;
+  assign gpio_i[61] = 'h0;
+  assign gpio_i[60] = 'h0;
 
   // tsw-part-2 gpio - 59:57
 
@@ -252,7 +252,7 @@ module system_top (
 
   // unused gpio - 55:53
 
-  assign gpio_i[55:53] = gpio_o[55:53];
+  assign gpio_i[55:53] = 'h0;
 
   // rf & clock-select gpio - 52:51
 
diff --git a/projects/adrv9371x/a10gx/system_top.v b/projects/adrv9371x/a10gx/system_top.v
index 74ebe9f39..cb6b4882c 100644
--- a/projects/adrv9371x/a10gx/system_top.v
+++ b/projects/adrv9371x/a10gx/system_top.v
@@ -136,10 +136,10 @@ module system_top (
 
   // gpio (ad9371)
 
-  assign gpio_i[63:61] = gpio_o[63:61];
+  assign gpio_i[63:61] = 'h0;
 
   assign dac_fifo_bypass = gpio_o[60];
-  assign gpio_i[60:60] = gpio_o[60];
+  assign gpio_i[60:60] = 'h0;
 
   assign ad9528_reset_b = gpio_o[59];
   assign ad9528_sysref_req = gpio_o[58];
@@ -149,11 +149,11 @@ module system_top (
   assign ad9371_rx2_enable = gpio_o[54];
   assign ad9371_test = gpio_o[53];
   assign ad9371_reset_b = gpio_o[52];
-  assign gpio_i[59:52] = gpio_o[59:52];
+  assign gpio_i[59:52] = 'h0;
 
   assign gpio_i[51:51] = ad9371_gpint;
 
-  assign gpio_i[50:32] = gpio_o[50:32];
+  assign gpio_i[50:32] = 'h0;
 
   // board stuff
 
@@ -163,9 +163,9 @@ module system_top (
 
   assign ddr3_a[14:12] = 3'd0;
 
-  assign gpio_i[31:27] = gpio_o[31:27];
+  assign gpio_i[31:27] = 'h0;
   assign gpio_i[26:16] = gpio_bd_i;
-  assign gpio_i[15: 0] = gpio_o[15:0];
+  assign gpio_i[15: 0] = 'h0;
 
   assign gpio_bd_o = gpio_o[15:0];
 
diff --git a/projects/adrv9371x/a10soc/system_top.v b/projects/adrv9371x/a10soc/system_top.v
index 5969ac59a..c0891b7c3 100644
--- a/projects/adrv9371x/a10soc/system_top.v
+++ b/projects/adrv9371x/a10soc/system_top.v
@@ -175,10 +175,10 @@ module system_top (
 
   // gpio (ad9371)
 
-  assign gpio_i[63:61] = gpio_o[63:61];
+  assign gpio_i[63:61] = 'h0;
 
   assign dac_fifo_bypass = gpio_o[60];
-  assign gpio_i[60:60] = gpio_o[60];
+  assign gpio_i[60:60] = 'h0;
 
   assign ad9528_reset_b = gpio_o[59];
   assign ad9528_sysref_req = gpio_o[58];
@@ -188,19 +188,19 @@ module system_top (
   assign ad9371_rx2_enable = gpio_o[54];
   assign ad9371_test = gpio_o[53];
   assign ad9371_reset_b = gpio_o[52];
-  assign gpio_i[59:52] = gpio_o[59:52];
+  assign gpio_i[59:52] = 'h0;
 
   assign gpio_i[51:51] = ad9371_gpint;
 
-  assign gpio_i[50:32] = gpio_o[50:32];
+  assign gpio_i[50:32] = 'h0;
   
   // board stuff (max-v-u21)
 
-  assign gpio_i[31:14] = gpio_o[31:14];
+  assign gpio_i[31:14] = 'h0;
   assign gpio_i[13:13] = sys_ddr_cal_success;
   assign gpio_i[12:12] = sys_ddr_cal_fail;
   assign gpio_i[11: 4] = gpio_bd_i;
-  assign gpio_i[ 3: 0] = gpio_o[3:0];
+  assign gpio_i[ 3: 0] = 'h0;
 
   assign gpio_bd_o = gpio_o[3:0];
 
diff --git a/projects/adrv9371x/kcu105/system_top.v b/projects/adrv9371x/kcu105/system_top.v
index 43856e2db..868422c88 100644
--- a/projects/adrv9371x/kcu105/system_top.v
+++ b/projects/adrv9371x/kcu105/system_top.v
@@ -224,8 +224,8 @@ module system_top (
     .dio_o (gpio_i[16:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[31:17] = gpio_o[31:17];
-  assign gpio_i[63:60] = gpio_o[63:60];
+  assign gpio_i[31:17] = 'h0;
+  assign gpio_i[63:60] = 'h0;
 
   system_wrapper i_system_wrapper (
     .dac_fifo_bypass (gpio_o[60]),
diff --git a/projects/adrv9371x/zc706/system_top.v b/projects/adrv9371x/zc706/system_top.v
index c060855d3..23f2f25b5 100644
--- a/projects/adrv9371x/zc706/system_top.v
+++ b/projects/adrv9371x/zc706/system_top.v
@@ -233,8 +233,8 @@ module system_top (
     .dio_o (gpio_i[14:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[31:15] = gpio_o[31:15];
-  assign gpio_i[63:60] = gpio_o[63:60];
+  assign gpio_i[31:15] = 'h0;
+  assign gpio_i[63:60] = 'h0;
 
   system_wrapper i_system_wrapper (
     .dac_fifo_bypass (gpio_o[60]),
diff --git a/projects/adrv9371x/zcu102/system_top.v b/projects/adrv9371x/zcu102/system_top.v
index 9f95081a5..f4a9e2602 100644
--- a/projects/adrv9371x/zcu102/system_top.v
+++ b/projects/adrv9371x/zcu102/system_top.v
@@ -179,10 +179,10 @@ module system_top (
               ad9371_gpio_16,       // 33
               ad9371_gpio_18}));    // 32
 
-  assign gpio_i[ 7: 0] = gpio_o[ 7: 0];
+  assign gpio_i[ 7: 0] = 'h0;
   assign gpio_i[20: 8] = gpio_bd_i;
-  assign gpio_i[31:21] = gpio_o[31:21];
-  assign gpio_i[94:60] = gpio_o[94:60];
+  assign gpio_i[31:21] = 'h0;
+  assign gpio_i[94:60] = 'h0;
 
   assign gpio_bd_o = gpio_o[ 7: 0];
 
diff --git a/projects/adv7511/zc702/system_top.v b/projects/adv7511/zc702/system_top.v
index b9100f476..acaabbf27 100644
--- a/projects/adv7511/zc702/system_top.v
+++ b/projects/adv7511/zc702/system_top.v
@@ -87,7 +87,7 @@ module system_top (
     .dio_o (gpio_i[15:0]),
     .dio_p ({gpio_bd[7:4], gpio_bd[15:8], gpio_bd[3:0]}));
 
-  assign gpio_i[63:16] = gpio_o[63:16];
+  assign gpio_i[63:16] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr_addr (ddr_addr),
diff --git a/projects/adv7511/zc706/system_top.v b/projects/adv7511/zc706/system_top.v
index 26aab8f1e..b25aebbe5 100644
--- a/projects/adv7511/zc706/system_top.v
+++ b/projects/adv7511/zc706/system_top.v
@@ -89,7 +89,7 @@ module system_top (
     .dio_o(gpio_i[14:0]),
     .dio_p(gpio_bd));
 
-  assign gpio_i[63:15] = gpio_o[63:15];
+  assign gpio_i[63:15] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr_addr (ddr_addr),
diff --git a/projects/adv7511/zed/system_top.v b/projects/adv7511/zed/system_top.v
index cee49ec7c..f65508d27 100644
--- a/projects/adv7511/zed/system_top.v
+++ b/projects/adv7511/zed/system_top.v
@@ -95,7 +95,7 @@ module system_top (
   wire    [ 1:0]  iic_mux_sda_o_s;
   wire            iic_mux_sda_t_s;
 
-  assign gpio_i[63:32] = gpio_o[63:32];
+  assign gpio_i[63:32] = 'h0;
 
   // instantiations
 
diff --git a/projects/cn0363/zed/system_top.v b/projects/cn0363/zed/system_top.v
index 3ebe27cc8..a2fcd2f46 100644
--- a/projects/cn0363/zed/system_top.v
+++ b/projects/cn0363/zed/system_top.v
@@ -111,8 +111,8 @@ module system_top (
   assign gain1_o = gpio_o[33];
 
   assign gpio_i[34] = spi_sdi; // Interrupt
-  assign gpio_i[33] = gpio_o[33];
-  assign gpio_i[32] = gpio_o[32];
+  assign gpio_i[33] = 'h0;
+  assign gpio_i[32] = 'h0;
   assign led_clk_o = excitation;
 
   ad_iobuf #(
diff --git a/projects/daq2/a10gx/system_top.v b/projects/daq2/a10gx/system_top.v
index 4a0bb4d3f..e8d0ae78d 100644
--- a/projects/daq2/a10gx/system_top.v
+++ b/projects/daq2/a10gx/system_top.v
@@ -155,21 +155,21 @@ module system_top (
 
   // gpio in & out are separate cores
 
-  assign gpio_i[63:44] = gpio_o[63:44];
+  assign gpio_i[63:44] = 'h0;
   assign dac_fifo_bypass = gpio_o[44];
   assign gpio_i[43:43] = trig;
 
-  assign gpio_i[42:40] = gpio_o[42:40];
+  assign gpio_i[42:40] = 'h0;
   assign adc_pd = gpio_o[42];
   assign dac_txen = gpio_o[41];
   assign dac_reset = gpio_o[40];
 
-  assign gpio_i[39:39] = gpio_o[39];
+  assign gpio_i[39:39] = 'h0;
 
-  assign gpio_i[38:38] = gpio_o[38];
+  assign gpio_i[38:38] = 'h0;
   assign clkd_sync = gpio_o[38];
 
-  assign gpio_i[37:37] = gpio_o[37];
+  assign gpio_i[37:37] = 'h0;
   assign gpio_i[36:36] = adc_fdb;
   assign gpio_i[35:35] = adc_fda;
   assign gpio_i[34:34] = dac_irq;
@@ -183,9 +183,9 @@ module system_top (
 
   assign ddr3_a[14:12] = 3'd0;
 
-  assign gpio_i[31:27] = gpio_o[31:27];
+  assign gpio_i[31:27] = 'h0;
   assign gpio_i[26:16] = gpio_bd_i;
-  assign gpio_i[15: 0] = gpio_o[15:0];
+  assign gpio_i[15: 0] = 'h0;
 
   assign gpio_bd_o = gpio_o[15:0];
 
diff --git a/projects/daq2/a10soc/system_top.v b/projects/daq2/a10soc/system_top.v
index e1c679939..87484dd8e 100644
--- a/projects/daq2/a10soc/system_top.v
+++ b/projects/daq2/a10soc/system_top.v
@@ -190,22 +190,22 @@ module system_top (
 
   // gpio in & out are separate cores
 
-  assign gpio_i[63:45] = gpio_o[63:45];
+  assign gpio_i[63:45] = 'h0;
   assign dac_fifo_bypass = gpio_o[44];
-  assign gpio_i[44:44] = gpio_o[44];
+  assign gpio_i[44:44] = 'h0;
   assign gpio_i[43:43] = trig;
 
-  assign gpio_i[42:40] = gpio_o[42:40];
+  assign gpio_i[42:40] = 'h0;
   assign adc_pd = gpio_o[42];
   assign dac_txen = gpio_o[41];
   assign dac_reset = gpio_o[40];
 
-  assign gpio_i[39:39] = gpio_o[39];
+  assign gpio_i[39:39] = 'h0;
 
-  assign gpio_i[38:38] = gpio_o[38];
+  assign gpio_i[38:38] = 'h0;
   assign clkd_sync = gpio_o[38];
 
-  assign gpio_i[37:37] = gpio_o[37];
+  assign gpio_i[37:37] = 'h0;
   assign gpio_i[36:36] = adc_fdb;
   assign gpio_i[35:35] = adc_fda;
   assign gpio_i[34:34] = dac_irq;
@@ -213,9 +213,9 @@ module system_top (
  
   // board stuff (max-v-u21)
 
-  assign gpio_i[31:12] = gpio_o[31:12];
+  assign gpio_i[31:12] = 'h0;
   assign gpio_i[11: 4] = gpio_bd_i;
-  assign gpio_i[ 3: 0] = gpio_o[3:0];
+  assign gpio_i[ 3: 0] = 'h0;
 
   assign gpio_bd_o = gpio_o[3:0];
 
diff --git a/projects/daq2/kc705/system_top.v b/projects/daq2/kc705/system_top.v
index 5743471c3..e106b0f72 100644
--- a/projects/daq2/kc705/system_top.v
+++ b/projects/daq2/kc705/system_top.v
@@ -228,10 +228,10 @@ module system_top (
     .dio_o (gpio_i[16:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:44] = gpio_o[63:44];
-  assign gpio_i[39] = gpio_o[39];
-  assign gpio_i[37] = gpio_o[37];
-  assign gpio_i[31:17] = gpio_o[31:17];
+  assign gpio_i[63:44] = 'h0;
+  assign gpio_i[39] = 'h0;
+  assign gpio_i[37] = 'h0;
+  assign gpio_i[31:17] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr3_addr (ddr3_addr),
diff --git a/projects/daq2/kcu105/system_top.v b/projects/daq2/kcu105/system_top.v
index 4afb09275..0b68cd1be 100644
--- a/projects/daq2/kcu105/system_top.v
+++ b/projects/daq2/kcu105/system_top.v
@@ -210,10 +210,10 @@ module system_top (
     .dio_o (gpio_i[16:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:44] = gpio_o[63:44];
-  assign gpio_i[39] = gpio_o[39];
-  assign gpio_i[37] = gpio_o[37];
-  assign gpio_i[31:17] = gpio_o[31:17];
+  assign gpio_i[63:44] = 'h0;
+  assign gpio_i[39] = 'h0;
+  assign gpio_i[37] = 'h0;
+  assign gpio_i[31:17] = 'h0;
 
   system_wrapper i_system_wrapper (
     .c0_ddr4_act_n (ddr4_act_n),
diff --git a/projects/daq2/vc707/system_top.v b/projects/daq2/vc707/system_top.v
index adf8accaa..024da4b14 100644
--- a/projects/daq2/vc707/system_top.v
+++ b/projects/daq2/vc707/system_top.v
@@ -222,10 +222,10 @@ module system_top (
     .dio_o (gpio_i[20:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:44] = gpio_o[63:44];
-  assign gpio_i[39] = gpio_o[39];
-  assign gpio_i[37] = gpio_o[37];
-  assign gpio_i[31:21] = gpio_o[31:21];
+  assign gpio_i[63:44] = 'h0;
+  assign gpio_i[39] = 'h0;
+  assign gpio_i[37] = 'h0;
+  assign gpio_i[31:21] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr3_addr (ddr3_addr),
diff --git a/projects/daq2/zc706/system_top.v b/projects/daq2/zc706/system_top.v
index 3e2bab14c..18f60a308 100644
--- a/projects/daq2/zc706/system_top.v
+++ b/projects/daq2/zc706/system_top.v
@@ -229,10 +229,10 @@ module system_top (
     .dio_o (gpio_i[14:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:44] = gpio_o[63:44];
-  assign gpio_i[39] = gpio_o[39];
-  assign gpio_i[37] = gpio_o[37];
-  assign gpio_i[31:15] = gpio_o[31:15];
+  assign gpio_i[63:44] = 'h0;
+  assign gpio_i[39] = 'h0;
+  assign gpio_i[37] = 'h0;
+  assign gpio_i[31:15] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr3_addr (ddr3_addr),
diff --git a/projects/daq2/zcu102/system_top.v b/projects/daq2/zcu102/system_top.v
index a06490c6b..6404a221c 100644
--- a/projects/daq2/zcu102/system_top.v
+++ b/projects/daq2/zcu102/system_top.v
@@ -154,16 +154,16 @@ module system_top (
   assign clkd_sync = gpio_o[38];
   assign gpio_bd_o = gpio_o[7:0];
 
-  assign gpio_i[94:44] = gpio_o[94:44];
+  assign gpio_i[94:44] = 'h0;
   assign gpio_i[43:43] = trig;
-  assign gpio_i[42:37] = gpio_o[42:37];
+  assign gpio_i[42:37] = 'h0;
   assign gpio_i[36:36] = adc_fdb;
   assign gpio_i[35:35] = adc_fda;
   assign gpio_i[34:34] = dac_irq;
   assign gpio_i[33:32] = clkd_status;
-  assign gpio_i[31:21] = gpio_o[31:21];
+  assign gpio_i[31:21] = 'h0;
   assign gpio_i[20: 8] = gpio_bd_i;
-  assign gpio_i[ 7: 0] = gpio_o[7:0];
+  assign gpio_i[ 7: 0] = 'h0;
 
   system_wrapper i_system_wrapper (
     .gpio_i (gpio_i),
diff --git a/projects/daq3/a10gx/system_top.v b/projects/daq3/a10gx/system_top.v
index c064e45d3..248e4a689 100644
--- a/projects/daq3/a10gx/system_top.v
+++ b/projects/daq3/a10gx/system_top.v
@@ -149,12 +149,12 @@ module system_top (
 
   // gpio in & out are separate cores
 
-  assign gpio_i[63:40] = gpio_o[63:40];
+  assign gpio_i[63:40] = 'h0;
   assign dac_fifo_bypass = gpio_o[41];
   assign sysref = gpio_o[40];
   assign gpio_i[39:39] = trig;
 
-  assign gpio_i[38:37] = gpio_o[38:37];
+  assign gpio_i[38:37] = 'h0;
   assign adc_pd = gpio_o[38];
   assign dac_txen = gpio_o[37];
 
@@ -171,9 +171,9 @@ module system_top (
 
   assign ddr3_a[14:12] = 3'd0;
 
-  assign gpio_i[31:27] = gpio_o[31:27];
+  assign gpio_i[31:27] = 'h0;
   assign gpio_i[26:16] = gpio_bd_i;
-  assign gpio_i[15: 0] = gpio_o[15:0];
+  assign gpio_i[15: 0] = 'h0;
 
   assign gpio_bd_o = gpio_o[15:0];
 
diff --git a/projects/daq3/kcu105/system_top.v b/projects/daq3/kcu105/system_top.v
index 04278961e..cbc55f858 100644
--- a/projects/daq3/kcu105/system_top.v
+++ b/projects/daq3/kcu105/system_top.v
@@ -213,8 +213,8 @@ module system_top (
     .dio_o (gpio_i[16:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:40] = gpio_o[63:40];
-  assign gpio_i[31:17] = gpio_o[31:17];
+  assign gpio_i[63:40] = 'h0;
+  assign gpio_i[31:17] = 'h0;
 
   system_wrapper i_system_wrapper (
     .c0_ddr4_act_n (ddr4_act_n),
diff --git a/projects/daq3/zc706/system_top.v b/projects/daq3/zc706/system_top.v
index e7aadc30f..05754cb47 100644
--- a/projects/daq3/zc706/system_top.v
+++ b/projects/daq3/zc706/system_top.v
@@ -233,8 +233,8 @@ module system_top (
     .dio_o (gpio_i[14:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:40] = gpio_o[63:40];
-  assign gpio_i[31:15] = gpio_o[31:15];
+  assign gpio_i[63:40] = 'h0;
+  assign gpio_i[31:15] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr3_addr (ddr3_addr),
diff --git a/projects/daq3/zcu102/system_top.v b/projects/daq3/zcu102/system_top.v
index 8124fa19b..83769f8d3 100644
--- a/projects/daq3/zcu102/system_top.v
+++ b/projects/daq3/zcu102/system_top.v
@@ -159,16 +159,16 @@ module system_top (
   assign clkd_sync = gpio_o[38];
   assign gpio_bd_o = gpio_o[7:0];
 
-  assign gpio_i[94:44] = gpio_o[94:44];
+  assign gpio_i[94:44] = 'h0;
   assign gpio_i[43:43] = trig;
-  assign gpio_i[42:37] = gpio_o[42:37];
+  assign gpio_i[42:37] = 'h0;
   assign gpio_i[36:36] = adc_fdb;
   assign gpio_i[35:35] = adc_fda;
   assign gpio_i[34:34] = dac_irq;
   assign gpio_i[33:32] = clkd_status;
-  assign gpio_i[31:21] = gpio_o[31:21];
+  assign gpio_i[31:21] = 'h0;
   assign gpio_i[20: 8] = gpio_bd_i;
-  assign gpio_i[ 7: 0] = gpio_o[7:0];
+  assign gpio_i[ 7: 0] = 'h0;
 
   system_wrapper i_system_wrapper (
     .gpio_i (gpio_i),
diff --git a/projects/fmcadc2/vc707/system_top.v b/projects/fmcadc2/vc707/system_top.v
index d8024eb58..05a00493b 100644
--- a/projects/fmcadc2/vc707/system_top.v
+++ b/projects/fmcadc2/vc707/system_top.v
@@ -172,8 +172,8 @@ module system_top (
     .dio_o (gpio_i[20:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:34] = gpio_o[63:34];
-  assign gpio_i[31:21] = gpio_o[31:21];
+  assign gpio_i[63:34] = 'h0;
+  assign gpio_i[31:21] = 'h0;
 
   ad_sysref_gen i_sysref (
     .core_clk (rx_clk),
diff --git a/projects/fmcadc2/zc706/system_top.v b/projects/fmcadc2/zc706/system_top.v
index 64b94fa42..698e8f8d4 100644
--- a/projects/fmcadc2/zc706/system_top.v
+++ b/projects/fmcadc2/zc706/system_top.v
@@ -180,8 +180,8 @@ module system_top (
     .dio_o (gpio_i[14:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:34] = gpio_o[63:34];
-  assign gpio_i[31:15] = gpio_o[31:15];
+  assign gpio_i[63:34] = 'h0;
+  assign gpio_i[31:15] = 'h0;
 
   ad_sysref_gen i_sysref (
     .core_clk (rx_clk),
diff --git a/projects/fmcadc4/zc706/system_top.v b/projects/fmcadc4/zc706/system_top.v
index 6cd4a2a63..bf93c1eab 100644
--- a/projects/fmcadc4/zc706/system_top.v
+++ b/projects/fmcadc4/zc706/system_top.v
@@ -197,8 +197,8 @@ module system_top (
     .dio_o (gpio_i[14:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:38] = gpio_o[63:38];
-  assign gpio_i[31:15] = gpio_o[31:15];
+  assign gpio_i[63:38] = 'h0;
+  assign gpio_i[31:15] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr3_addr (ddr3_addr),
diff --git a/projects/fmcjesdadc1/kc705/system_top.v b/projects/fmcjesdadc1/kc705/system_top.v
index 15e18cc43..72500e911 100644
--- a/projects/fmcjesdadc1/kc705/system_top.v
+++ b/projects/fmcjesdadc1/kc705/system_top.v
@@ -134,8 +134,8 @@ module system_top (
     .dio_o (gpio_i[16:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:32] = gpio_o[63:32];
-  assign gpio_i[31:17] = gpio_o[31:17];
+  assign gpio_i[63:32] = 'h0;
+  assign gpio_i[31:17] = 'h0;
 
   fmcjesdadc1_spi i_fmcjesdadc1_spi (
     .spi_csn (spi_csn[0]),
diff --git a/projects/fmcjesdadc1/vc707/system_top.v b/projects/fmcjesdadc1/vc707/system_top.v
index 66f8c7b2d..b0ffef7b2 100644
--- a/projects/fmcjesdadc1/vc707/system_top.v
+++ b/projects/fmcjesdadc1/vc707/system_top.v
@@ -131,8 +131,8 @@ module system_top (
     .dio_o (gpio_i[20:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:32] = gpio_o[63:32];
-  assign gpio_i[31:21] = gpio_o[31:21];
+  assign gpio_i[63:32] = 'h0;
+  assign gpio_i[31:21] = 'h0;
 
   fmcjesdadc1_spi i_fmcjesdadc1_spi (
     .spi_csn (spi_csn_0),
diff --git a/projects/fmcjesdadc1/zc706/system_top.v b/projects/fmcjesdadc1/zc706/system_top.v
index 4bae164d1..aeccc1dc3 100644
--- a/projects/fmcjesdadc1/zc706/system_top.v
+++ b/projects/fmcjesdadc1/zc706/system_top.v
@@ -120,8 +120,8 @@ module system_top (
     .dio_o (gpio_i[14:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:32] = gpio_o[63:32];
-  assign gpio_i[31:15] = gpio_o[31:15];
+  assign gpio_i[63:32] = 'h0;
+  assign gpio_i[31:15] = 'h0;
 
   assign spi_adc_clk = spi_clk;
   assign spi_clk_clk = spi_clk;
diff --git a/projects/fmcomms2/kc705/system_top.v b/projects/fmcomms2/kc705/system_top.v
index 70d0be4b8..b905acc1e 100644
--- a/projects/fmcomms2/kc705/system_top.v
+++ b/projects/fmcomms2/kc705/system_top.v
@@ -158,8 +158,8 @@ module system_top (
     .dio_o (gpio_i[16:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:47] = gpio_o[63:47];
-  assign gpio_i[31:17] = gpio_o[31:17];
+  assign gpio_i[63:47] = 'h0;
+  assign gpio_i[31:17] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr3_addr (ddr3_addr),
diff --git a/projects/fmcomms2/kcu105/system_top.v b/projects/fmcomms2/kcu105/system_top.v
index 3500bfb5e..c5378fcfb 100644
--- a/projects/fmcomms2/kcu105/system_top.v
+++ b/projects/fmcomms2/kcu105/system_top.v
@@ -130,9 +130,9 @@ module system_top (
     .dio_o (gpio_i[16:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:40] = gpio_o[63:40];
+  assign gpio_i[63:40] = 'h0;
   assign gpio_i[39:32] = gpio_status;
-  assign gpio_i[31:17] = gpio_0[31:17];
+  assign gpio_i[31:17] = 'h0;
 
   system_wrapper i_system_wrapper (
     .c0_ddr4_act_n (ddr4_act_n),
diff --git a/projects/fmcomms2/vc707/system_top.v b/projects/fmcomms2/vc707/system_top.v
index 655c7390a..61b0e886a 100644
--- a/projects/fmcomms2/vc707/system_top.v
+++ b/projects/fmcomms2/vc707/system_top.v
@@ -148,8 +148,8 @@ module system_top (
     .dio_o (gpio_i[20:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:47] = gpio_o[63:47];
-  assign gpio_i[31:21] = gpio_o[31:21];
+  assign gpio_i[63:47] = 'h0;
+  assign gpio_i[31:21] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr3_addr (ddr3_addr),
diff --git a/projects/fmcomms2/zc702/system_top.v b/projects/fmcomms2/zc702/system_top.v
index 0eb4dc263..1b2d0509b 100644
--- a/projects/fmcomms2/zc702/system_top.v
+++ b/projects/fmcomms2/zc702/system_top.v
@@ -137,10 +137,10 @@ module system_top (
     .dio_o ({gpio_i[15:12], gpio_i[7:0]}),
     .dio_p ({gpio_bd[7:4], gpio_bd[11:8], gpio_bd[3:0]}));
 
-  assign gpio_i[63:51] = gpio_o[63:51];
-  assign gpio_i[48:47] = gpio_o[48:47];
-  assign gpio_i[31:16] = gpio_o[31:16];
-  assign gpio_i[11: 8] = gpio_o[11 :8];
+  assign gpio_i[63:51] = 'h0;
+  assign gpio_i[48:47] = 'h0;
+  assign gpio_i[31:16] = 'h0;
+  assign gpio_i[11: 8] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr_addr (ddr_addr),
diff --git a/projects/fmcomms2/zc706/system_top.v b/projects/fmcomms2/zc706/system_top.v
index d56a252f8..f3c56b81e 100644
--- a/projects/fmcomms2/zc706/system_top.v
+++ b/projects/fmcomms2/zc706/system_top.v
@@ -159,9 +159,9 @@ module system_top (
     .dio_o (gpio_i[14:0]),
     .dio_p (gpio_bd));
 
-  assign gpio_i[63:51] = gpio_o[63:51];
-  assign gpio_i[48:47] = gpio_o[48:47];
-  assign gpio_i[31:15] = gpio_o[31:15];
+  assign gpio_i[63:51] = 'h0;
+  assign gpio_i[48:47] = 'h0;
+  assign gpio_i[31:15] = 'h0;
 
   ad_iobuf #(.DATA_WIDTH(1)) i_iobuf_tdd_sync (
     .dio_t (tdd_sync_t),
diff --git a/projects/fmcomms2/zcu102/system_top.v b/projects/fmcomms2/zcu102/system_top.v
index 8ca9ce70c..b3872d761 100644
--- a/projects/fmcomms2/zcu102/system_top.v
+++ b/projects/fmcomms2/zcu102/system_top.v
@@ -81,9 +81,9 @@ module system_top (
   assign gpio_ctl = gpio_o[43:40];
   assign gpio_bd_o = gpio_o[20:13];
 
-  assign gpio_i[95:40] = gpio_o[95:40];
+  assign gpio_i[95:40] = 'h0;
   assign gpio_i[39:32] = gpio_status;
-  assign gpio_i[31:13] = gpio_o[31:13];
+  assign gpio_i[31:13] = 'h0;
   assign gpio_i[12: 0] = gpio_bd_i;
 
   assign spi_csn = spi0_csn[0];
diff --git a/projects/fmcomms2/zed/system_top.v b/projects/fmcomms2/zed/system_top.v
index 7892fa26a..79f83ec59 100644
--- a/projects/fmcomms2/zed/system_top.v
+++ b/projects/fmcomms2/zed/system_top.v
@@ -144,8 +144,8 @@ module system_top (
               gpio_status,
               gpio_bd}));
 
-  assign gpio_i[63:51] = gpio_o[63:51];
-  assign gpio_i[48:47] = gpio_o[48:47];
+  assign gpio_i[63:51] = 'h0;
+  assign gpio_i[48:47] = 'h0;
 
    ad_iobuf #(.DATA_WIDTH(2)) i_iobuf_iic_scl (
     .dio_t ({iic_mux_scl_t_s,iic_mux_scl_t_s}),
diff --git a/projects/fmcomms5/zc702/system_top.v b/projects/fmcomms5/zc702/system_top.v
index c5af21f01..c1d4cddd9 100644
--- a/projects/fmcomms5/zc702/system_top.v
+++ b/projects/fmcomms5/zc702/system_top.v
@@ -217,8 +217,8 @@ module system_top (
   assign spi_clk = spi0_clk;
   assign spi_mosi = spi0_mosi;
   assign spi0_miso = spi_miso;
-  assign gpio_i[63:60] = gpio_o[63:60];
-  assign gpio_i[45:44] = gpio_o[45:44];
+  assign gpio_i[63:60] = 'h0;
+  assign gpio_i[45:44] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr_addr (ddr_addr),
diff --git a/projects/fmcomms5/zc706/system_top.v b/projects/fmcomms5/zc706/system_top.v
index d092f820f..5884a63f0 100644
--- a/projects/fmcomms5/zc706/system_top.v
+++ b/projects/fmcomms5/zc706/system_top.v
@@ -212,9 +212,9 @@ module system_top (
   assign spi_clk = spi0_clk;
   assign spi_mosi = spi0_mosi;
   assign spi0_miso = spi_miso;
-  assign gpio_i[63:60] = gpio_o[63:60];
-  assign gpio_i[45:44] = gpio_o[45:44];
-  assign gpio_i[15] = gpio_o[15];
+  assign gpio_i[63:60] = 'h0;
+  assign gpio_i[45:44] = 'h0;
+  assign gpio_i[15] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr_addr (ddr_addr),
diff --git a/projects/fmcomms5/zcu102/system_top.v b/projects/fmcomms5/zcu102/system_top.v
index 189056be6..c3342aa85 100644
--- a/projects/fmcomms5/zcu102/system_top.v
+++ b/projects/fmcomms5/zcu102/system_top.v
@@ -167,12 +167,12 @@ module system_top (
   assign gpio_ctl_0 = gpio_o[41:38];
   assign gpio_bd_o = gpio_o[20:13];
   assign gpio_i[12: 0] = gpio_bd_i;
-  assign gpio_i[21:13] = gpio_o[21:13];
+  assign gpio_i[21:13] = 'h0;
   assign gpio_i[29:22] = gpio_status_0;
   assign gpio_i[37:30] = gpio_status_1;
-  assign gpio_i[63:38] = gpio_o[63:38];
+  assign gpio_i[63:38] = 'h0;
   assign gpio_i[64] = gpio_ad5355_lock;
-  assign gpio_i[94:65] = gpio_o[94:65];
+  assign gpio_i[94:65] = 'h0;
 
   assign spi_ad9361_0 = spi0_csn[0];
   assign spi_ad9361_1 = spi0_csn[1];
diff --git a/projects/imageon/zed/system_top.v b/projects/imageon/zed/system_top.v
index d33afbc40..aaf517c42 100644
--- a/projects/imageon/zed/system_top.v
+++ b/projects/imageon/zed/system_top.v
@@ -100,7 +100,7 @@ module system_top (
   wire    [ 1:0]  iic_mux_sda_o_s;
   wire            iic_mux_sda_t_s;
 
-  assign gpio_i[63:34] = gpio_o[63:34];
+  assign gpio_i[63:34] = 'h0;
 
   // instantiations
 
diff --git a/projects/motcon2_fmc/zed/system_top.v b/projects/motcon2_fmc/zed/system_top.v
index 613e74829..a08103d37 100644
--- a/projects/motcon2_fmc/zed/system_top.v
+++ b/projects/motcon2_fmc/zed/system_top.v
@@ -174,8 +174,8 @@ module system_top (
   assign pwm_m2_dh_o    = 1'b0;
   assign pwm_m2_dl_o    = 1'b0;
 
-  assign gpio_i[63:35]  = gpio_o[63:35];
-  assign gpio_i[32]     = gpio_o[32];
+  assign gpio_i[63:35]  = 'h0;
+  assign gpio_i[32]     = 'h0;
 
   // instantiations
 
diff --git a/projects/pluto/system_top.v b/projects/pluto/system_top.v
index 8b74dae15..4757aeaeb 100644
--- a/projects/pluto/system_top.v
+++ b/projects/pluto/system_top.v
@@ -92,7 +92,7 @@ module system_top (
   wire    [16:0]  gpio_o;
   wire    [16:0]  gpio_t;
 
-  assign gpio_i[16:15] = gpio_o[16:15];
+  assign gpio_i[16:15] = 'h0;
   // instantiations
 
   ad_iobuf #(.DATA_WIDTH(15)) i_iobuf (
diff --git a/projects/sidekiqz2/system_top.v b/projects/sidekiqz2/system_top.v
index e408970c1..e2dea3d3f 100755
--- a/projects/sidekiqz2/system_top.v
+++ b/projects/sidekiqz2/system_top.v
@@ -102,7 +102,7 @@ module system_top (
               gpio_ctl,           // 11: 8
               gpio_status}));     //  7: 0
 
-  assign gpio_i[18:17] = gpio_o[18:17];
+  assign gpio_i[18:17] = 'h0;
 
   system_wrapper i_system_wrapper (
     .ddr_addr (ddr_addr),