= HF8V = / = SP8WJT = / = SP0106RZ =

HF-12244


PROJECT: HF-12244
DESCRIPTION: Universal Microprocessor Module M50744
STATUS: p
PROJECT START DATE: 2023
LOCALISATION: PI
DOCUMENTATION: TM
PCB: TPD42425
DIMENSIONS:

CPU: M50744
CPU BRAND: MITSUBISHI
ARCHITECTURE: MELPS740
ROM: 4K
RAM: 144
CLOCK: 4 MHz (2us/instr.)
ADR SPC: 64K
CPU CATALOG NUMBER: UC-391
THN ADDRESS: 0x2B
UC TYPE: 0xB6



Block diagram





Project Info

This is another retro project, but on dedicated PCB. Kit prepared, PCB cutted but production not started yet.
I already wrote some code for this project. Even if this uC is very slow for nowadays (near 0.5 MIPS) it has 64KB memory space, so it is possible to translate my THOS-1 operating system for it.

There are four modes of operation, where microprocessor mode is most interesting for me. Switching to microprocessor mode is simple: CNVSS (pin 27) must be connected to VCC. It is important detail, because some uCs can use some kind of security features to block further expansion, but in 1980's such stupid (typically capitalistic) ideas where still not widely used by designers (today these guys can block even erasing user code what has nothing to do with user code security but rather with greedy - working uC cannot be reused again).

MELPS740 architecture is quite good made, there is so called zero page for RAM and special page (last page) for defined functions table. Because I'm also using this trick in my THOS-1 operating system I don't need to write software function for this. Thanks to such table HAVR instruction INT can reach all system functions with 2 bytes only in whole 16b address space.

Through the years I gathered small collection of MELPS740 microcontrollers, mainly from old consumer and bureau electronics:

UC-### MICROPROCESSOR NAME BRAND NAME FAMILY
(SUBFAMILY, CORE)		 DISPOSITION REMARKS THN ADR TYPE
UC-197 M50754 MITSUBISHI MELPS740 reserve ROM6144, RAM192, 4MHz, EXT 0x05 0xB6
UC-293 M38002 MITSUBISHI MELPS740 (3800) HF-17243 2MIPS, EXT 0x51 0xB6
UC-391 M50744 MITSUBISHI MELPS740 HF-12244 8b, ROM4K, RAM144, CLK 4MHz, ADR SPC 64K, EXT 0x2B 0xB6
UC-392 M50745 MITSUBISHI MELPS740 HF-17706 ROM6144, RAM192, 4MHz, EXT 0x27 0xB6
UC-526 DMB5208 (M50754) DAEWOO MELPS740 HF-17589->reserve ROM6144, RAM192, 4MHz, EXT 0x56 0xB6

Another MELPS740 retro systems are quite possible, but thats not concrete plans yet. I already wrote some assembler code in ASL and I found this rather well-made instruction set. I also wrote my own macro assembler but it is still not debugged.





Sources:
[1] Datasheet M50744
[2] MELPS740 Programming Manual
[3] MELPS740 Instructions


Prefix 122

HF Register

Microcontrollers in my constructions

UC Database - my CPU collection

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