Hi Wayne, it seems that the CPU is working correctly and it seems as if it is constantly executing instructions without writing or doing any IO. I wonder if it is just executing NOPs?
Are you sure the flash chip is programmed correctly? Have you been able to verify its content?
How about trying an EPROM or another flash chip?
Cheers!
Max
Sent from my iPad Hi All, Thanks for the help so far. Based on David's suggestions, i've put U10 & U14 back in, re-flashed the 29F040 with N8VEM_SW.003 and had a prod around with the scope. Just to get everyone on the same page, this is how the board is configured now, ignoring any previous posts: - CPU clock is 8Mhz
- U2 is 29F040-90 Flash chip
- ROM image is N8VEM_SW.003
- All jumpers are default except K6 & K8 due to U2 being flash
- Currently have U18, U21, U11, U8, U9 removed
- CPU is Z84C0020PEC
Tests: CPU: - I have both CPU Clock
- /RESET is high, confirmed it goes low for as long as the reset switch is held down
- /M1 pulsing @ 2MHz
- /MREQ pulsing @ 4Mhz
- /IORQ, /WR, /HALT, /WAIT, /INT, /NMI, /BUSAK, /BUSRQ are all high
- /RD is pulsing @ 2MHz
- /RFSH is pulsing around 2MHz
Flash - /CS_ROM is pulsing. the freq changes, but it is now a proper signal I believe Scope Capture
- The Data lines seem to be pulsing fine Scope Capture of A0
UART - I have UART clock
- I can see some of the Data lines D0-7 pulsing, some are low
- /CS_UART seems to be high all the time from power on. I wouldn't have expected the UART to be selected the whole time.
For those still with me down this far, thanks. Any pointers as to where to from here? Wayne.
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