1 Jul
2012
1 Jul
'12
12:14 p.m.
Here's an HP description from
http://www.bitsavers.org/pdf/hp/9000_dio/98642_HP-
DIO_Four_Channel_Mux_ERD_Sep84.pdf
(PDF page 24)
"The PHI signal is output from the Z80 clock driver circuitry,
which is a schottky clamped circuit using a PNP-NPN transistor (push-
pull) pair to obtain the required current and waveform to drive the
Z80 devices. "
Probably very similar to the Z80 clock driver shown here:
http://www.80bus.co.uk/pages/gemini/documentation/GM813_Circuit.pdf
--Chuck