February 21, 2022

Callan Multibus 68k CPU board - Using the Promice

An addendum up front. I am probably going to end up not using the promice. By removing the extension rom pair (which run the CWC boot loader), the standard boot roms now run the rom monitor, which includes an S-record download facility.

I want to do some experimenting with the Callan board. I have no way to load code onto it that I know of. I do have a Promice ROM emulator, and a dual unit that will emulate a pair of 8 bit devices in the arrangement the Callan uses, so this is my big chance to try it out.

I have used a plain old 8 bit Promice many many times, but this dual 16 bit business will be new. Much of the following will not be specific to the Callan.

Power jumpers

The manual says to always use external power and never let the target power the promice. So you install the Ext jumper and not the Rom jumper. If you are using fancy target probes, you always select the "32" jumper. In my case, using DIP probes, I need to select 24, 28, or 32. So I will have 2 jumpers in place for each section. The "Ext" jumper, and one of 24, 28, or 32.

Fancy pins/jumpers

There are a block of 10 pins that we can just ignore. These are used for two way "fancy" debugging protocols. Here they are just for the record: 
rst+/rst-  To target (we could use these)
int+/int-  To target from "AI" software
mwr/swr    To promice (write strobes)
req        To target (PiCOM protocol)
ack        To promice (PiCOM protocol)
inth       To promice (directly drives CTS to host)
Mwr is "master write" to D0-D7 (lower subunit).
Swr is "slave write" to D8-D15 (upper subunit).

Cables

There is a keyed pin 34 cable (two of them on my newer unit) that you use to connect to the host. The first thing to know about this cable is that pin 1 on the cable is not pin 1 on the ROM device. Pin 1 for the device comes from various places along the cable depending on the device, hence various cables. What is constant is that pin 34 on the promice connector is ground and will connect to the lowest left pin on whatever device (pin 14 for a 2764).

And a word to the wise. The cables with DIP ends are precious. So get a nice machine tool DIP socket and install it on the DIP pins. If damaged, the socket can be replaced. Also, it is quite easy to convert a 32 pin cable for 28 pin use, using some strip type machine tool headers. This has the additional advantage of raising up the ribbon cables to perhaps clear other parts on the target board.

Feedback? Questions? Drop me a line!

Tom's Computer Info / tom@mmto.org