Z80 ERROR: Difference between revisions

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A generic error message that occurs when the [[68k]] doesn't receive a reply from the [[Z80]] in time.
[[File:error_z80.png|thumb]]


Command byte $01 is sent to the Z80 when its program ROM needs to be changed, such as at power-on (switch from onboard [[SM1]] to cart [[M1 ROM]]) or when switching the active slot (changing which cart M1 ROM is selected). This command mutes [[YM2610]] audio and jumps to an infinite loop in RAM where it is then safe to switch the Z80 program ROM.  The Z80 sends the 68k $01 right before jumping to signal that it is safe to switch. If the $01 byte is never received, "Z80 ERROR" is displayed and the system locks up.
==Cause==


==Testing==
The {{Chipname|68k}} didn't receive a reply to command $01 from the {{Chipname|Z80}} in time. The Z80 doesn't test [[SM1]] ROM, its RAM nor the {{Chipname|YM2610}} but if any of those components are bad, they can prevent the Z80 from being able to reply which will then cause the error.


The Z80 doesn't test [[SM1]], its RAM or the [[YM2610]]. This error only covers bad [[68k/Z80 communication]], but if any of those components are bad, it can stop the Z80 from being able to reply which will then cause the error to be displayed.
==Suggestions==


==MV-1C==
* Check Z80 power, reset and clock
* Check Z80 work RAM
* Check {{Chipname|NEO-D0}} Z80 control lines
* Check Z80 data bus at {{Chipname|NEO-C1}}
* ...


This board displays this error with no cart inserted since it has no SM1 to control the Z80.
==MV1C==
 
The [[MV1C]] board displays this error with no cart inserted since it has no SM1 ROM. This is normal.


[[Category:Audio system]]
[[Category:Audio system]]
[[Category:Repairs]]
[[Category:Repairs]]

Revision as of 04:27, 12 October 2016

Cause

The 68k didn't receive a reply to command $01 from the Z80 in time. The Z80 doesn't test SM1 ROM, its RAM nor the YM2610 but if any of those components are bad, they can prevent the Z80 from being able to reply which will then cause the error.

Suggestions

  • Check Z80 power, reset and clock
  • Check Z80 work RAM
  • Check NEO-D0 Z80 control lines
  • Check Z80 data bus at NEO-C1
  • ...

MV1C

The MV1C board displays this error with no cart inserted since it has no SM1 ROM. This is normal.

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