*** M E M O R U M ***

Possible to connect Z80 signals direct to RAM:
/CE1 = /MREQ, CE2 = A15, /OE= /RD, /WE = /WR

Could do similar with 'ROM':
/CE = A15, /OE = /RD
if not bothered about I/O reads at all, or any input ports => 32768

74F32 would then not be needed.

I have taken the liberty of writing a short program to convert Martin's single source file to M80 format, as used at Memotech. The result assembles and links perfectly using M80 and L80 in CP/M.

To be truly authentic, you should use CP/M with M80 as your assembler and L80 as your linker because that's what we used at Memotech. In fact that's the combination I am using still, most recently last night.

Crazyboss wrote: they didn't know about the jp (hl) instruction ?

PUSH HL | ... | EX (SP),HL | RET preserves HL.

I was the last person at Memotech to modify the Noddy code before it was committed to mask ROM. Knowing how it was supposed to work would have been helpful! Although I didn't make the decisions it wasn't easy to choose 11 commands that spelt BIG EARS PLOD. Some names changed and initial letters were...

The 16-bit increment/decrement circuit explains how during refresh cycles bit 7 of R does not increment and why - to prevent the I register from incrementing too.

There is a lot of very interesting low-level information about the Z80 at Ken Shirriff's blog http://www.righto.com/ All the posts relating to the Z80 can be seen on one page at http://www.righto.com/search/label/Z-80 Future posts should be added at the top. As this page is rather large, here are li...

All the info I have on the HRX should appear on a well-known Memotech website in due course, but in the meantime here are a couple of teasers:

I worked for a company beginning with the letter M at Oxford and Witney in the 1980s.

The Rompak is a very simple device, consisting of an EPROM, a 47 nF decoupling capacitor and a half length 30-way edge connector. /GROM from the bus is connected to /CE and /OE of the EPROM, with A0-A12 and D0-D7 connected as one would expect. The masking tape is not for insulation, but to wedge the...