Z80 ERROR



=Causes=

The didn't receive a reply to command $01 from the  in time. The Z80 doesn't test the SM1 ROM, its RAM nor the but if any of those components are bad, they can prevent the Z80 from being able to reply which will then cause the error.

=Repair suggestions=

On MV1F boards, this error seems common due to trace cuts caused by a leaking battery. A few wires can solve the problem.


 * Check Z80 +5V supply, reset and clock signals
 * Check connectivity to Z80 work RAM
 * Check connectivity to SM1 ROM or cartridge's M1 ROM
 * Check Z80 control lines
 * Check Z80 data bus at

Note: Replacement SMT Z80s can be found in some Ti calculators :)

=MV1B=

The board displays this error when no cart inserted because it has no SM1 ROM. This is normal.