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ice40: Support for undriven / unconnected output ports

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If a port specified as output (and thus had a $nextpnr_obuf inserted)
is undriven (const `z` or const `x`), we make sure to not enable
the output driver. Also enable pull-ups if it was requested by the user.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
This commit is contained in:
Sylvain Munaut 2023-01-29 22:04:13 +01:00
parent 0cf5006e3b
commit f50d4c1ed1
1 changed files with 6 additions and 1 deletions
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7
ice40/cells.cc
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@ -411,7 +411,12 @@ void nxio_to_sb(Context *ctx, CellInfo *nxio, CellInfo *sbio, pool<IdString> &to
nxio->movePortTo(id_O, sbio, id_D_IN_0);
pull_up_attr = true;
} else if (nxio->type == ctx->id("$nextpnr_obuf")) {
sbio->params[id_PIN_TYPE] = 25;
NetInfo *i = nxio->getPort(id_I);
if (i == nullptr || i->driver.cell == nullptr) {
sbio->params[id_PIN_TYPE] = 1;
pull_up_attr = true;
} else
sbio->params[id_PIN_TYPE] = 25;
nxio->movePortTo(id_I, sbio, id_D_OUT_0);
} else if (nxio->type == ctx->id("$nextpnr_iobuf")) {
// N.B. tristate will be dealt with below