The micro-code in the HJS22 is implemented in five MM5203Q chips. To program these chips I had to built a programmer.
Here are some pictures of the programmer:
In 1976 I didn't had a PC so I had to program all 256 location by hand. One mistake and I had to erase the chip and start all over again.
The input and display of the programmer is octal, at that time I was unable to find a hex keyboard and hex displays.
One micro word is 40 bits. 8 bits for 'Next Address' and 32 bits to control the whole machine.
There are two micro word formats: Normal and Branch determined by bit 23. (see red circle)
NORMAL:
Bit 23 = 0. Bits 9 till 40 are defined as shown in the above figure.BRANCH:
Bit 23 = 1. Bits 9 till 16 form together the next micro word address if the condition selected by bits 17 - 20 is true.
If the condition is false the next micro word address is taken from bits 1 - 8.
Bits 22 and 24 till 40 are ignored. (must be all zero.)This pdf file (5 Mbyte) contains scanned pages of the hand writen micro code.
Pages 1 - 4 Detailed description micro-word layout.
Page 5 High level flow chart of the micro code.
Pages 6 - 13 8 pages micro code.
