Parallel Link Monitor

A safety-critical backplane carries the same 8-bit word on two parallel links, A and B. Your monitor compares them lane by lane and raises one clean verdict. Lanes flagged as "under maintenance" must never trigger it, because a technician is allowed to disturb those wires.

Interface

Port	Direction	Type	Description
`a`	in	8-bit vector	Word as received on link A
`b`	in	8-bit vector	Word as received on link B
`maint`	in	8-bit vector	'1' on each lane currently under maintenance
`diff`	out	8-bit vector	'1' on each lane where the links disagree
`ok`	out	1 bit	High when every lane agrees
`alert`	out	1 bit	High when any lane not under maintenance disagrees

Behavior

diff marks disagreement per lane: bit n is '1' exactly when bit n of a differs from bit n of b
ok is high when all eight lanes agree, that is, when no bit of diff is high
alert is high when at least one disagreeing lane is outside maintenance: disagreements on lanes marked in maint are filtered out before the verdict
A disagreement on a maintained lane therefore drops ok but leaves alert low; the testbench checks this case explicitly

Constraints

OPERATORS

only bitwise operators (and, or, xor, not / &, |, ^, ~) and reduction operators.

STRUCTURE

one concurrent assignment per output; no processes or always blocks.

combinational language-basics

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