SDD 7612fcbda9 reference: LANCE loopback-FCS datasheet evidence (MAME condition is right) ...

Add the Am7990 Technical Manual and Am79C90 datasheet to
reference/lance-datasheet/ and a report, reference/lance-loopback-fcs.md,
that answers whether MAME's am79c90 receive() FCS condition
(!(MODE_LOOP) || MODE_DTCR) is inverted.

Verdict: MAME is right. The CRC generator and checker share one circuit,
so with LOOP=1 the receiver can only check the FCS when DTCR=1 -- exactly
what MAME does. The proposed inversion would be wrong in both loopback
cases. No MAME change made.

2026-10-16 16:46:47 +03:00

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