The Interface card adds more memory (2x EPROM 2716, 1K RAM with 2x 2114), cassette interface, TTY interface, VIA 6522 interface.
Inspired by the KIM-1 and the Micro ADE cassette motor control. Note that the hardware TTY echo is now a jumper!
Software PM (Print Monitor, a serial interface monitor) and TM (Tape Monitor, to load/save KIM-1 compatible files on tape) and PM (Print Monir Extended).
EPROM ESS507 has PM, ESS507N has PM + PME, ESS506 has TM.
The bipolar ROM 82S33 has the name ESS508, it is used to decode memory for the various devices on the expansion card. A real problem device when constructing a new Junior!
See the Programming a 82S23 page how to program the 82S23.
Circuit diagram part 1, ROM, RAM, VIA
Circuit diagram part 2, TTY interface, audio cassette interface
The ROMS you need for an original Interface card are TM 506 and PM PME 507n.
Have a look at the Elektor Articles and Books page for a mullti-lingual overview of all publications on Elektor/Elektuur Junior and more.
Note that in old dumps of ROMs of TM there is a (harmless) error. On location it should be
0C21 C9 41 CMP #$41 ;IGNORE 3A…40
Instead is found
0C21 C9 14
which means the check is also OK with correct input. Perhaps this error was in the original ROM already and never noticed!
0717 0C19 ;*** ASCHEX *** 0718 0C19 ;CONVERT AN ASCII CHARACTER TO A HEX DATA NIBBLE. 0719 0C19 ;1) RETURN WITH CONVERTED HEX NUMBER IN ACCU 0720 0C19 ;2) N = 1, IF NOT VALID HEX NUMBER 0721 0C19 ;3) Z = 1, IF VALID HEX NUMBER 0722 0C19 ;4) *** ASCHEX IS ALSO USED IN THE PRINTER SOFTWARE *** 0723 0C19 C9 30 ASCHEX CMP #$30 ;IGNORE 00...2F 0724 0C1B 30 0C BMI NOTVAL 0725 0C1D C9 3A CMP #$3A 0726 0C1F 30 0B BMI VALID 0727 0C21 C9 41 CMP #$41 ;IGNORE 3A...40 0728 0C23 30 04 BMI NOTVAL 0729 0C25 C9 47 CMP #$47 ;IGNORE 47...7F 0730 0C27 30 03 BMI VALID
Interface card PCB front (note not on scale!)
Interface card PCB back (note not on scale!)
Interface card layout
Backplane PCB, part of it could be used to connect Junior PCB to Interface card.
User wikokim on the forum.classic-computing.de bought this system in 1978/79. And published the following documents and ...
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