Hello again Everyone,
Last night my roommate and I worked on dumping the Hayes Smartmodem 1200
firmware so that we could attempt a repair on another modem. This other
modem had a dead EPROM, a dead ROMless Z8, a dead CD4069, and a dead
'SR0075' (custom marked Hayes part with Zilog logo on it).
As it turns out, the SR0075 is a Z8 with 2kB of mask ROM. Attempts to
read it like an OTP/EPROM part did not work, however were were able to
put it in test mode, as detailed on page 363 of
By doing so, we were able to execute some simple code which read every
byte of the internal ROM and dumped it to memory address 0xAAAA, which
we then recorded with a logic analyzer to create the dump of this Z8.
The files are attached to this email, and it'd be nice if they were
archived somewhere. Maybe somewhere in bitsavers, if Al could help us
out with this. One file is the internal Z8 ROM, and the other is the
2764 that goes with the ROMless Z8.