To all interested in the MailStation.
I have read all the postings here and I decided to purchase one for myself and check it out.
After two days of searching the web, I have found docs for all the chips ( sans processor ). The chips listed by others did not tell the best story about the internals of this machine.
The RCV336ACF/SP is an old Rockwell chip. I found an old pdf manual for this chip. The manual is far from complete, however is shows the EPROM and 32K RAM chip as part of its design.
The EPROM and the RAM on the oposite side of the board work together with the 336 chip. The major part of this board is modem electronics.
The CPU and its memory chips looks to me as a simple processsor interface. The small FLASH( 29f080 ) looks like the code space. The Larger FLASH ( 28f040 ) is used for email storage. The RAM of course is working storage for the processor.
The modem and display:
Tracing the data lines from the processor memory section, I found that the display and modem are on a seprate data bus from the main memory buss. One of the 74HC245 devices isolates these busses from each other. ( I am sure its for drive capability )
The keyboard and printer port:
These lines connect directly to the CPU. With these many lines connected directly to the CPU, the memory buss must be left. I will be connecting my logic analyzer to the memory buss this week to check what the code looks like after RESET.
With over 20 years of Z80 code writting I am sure to notice if this is a real Z80 or not. The data lines from the 28F080 is only 8-bits wide. The READ and WRITE line of the two flash parts are connected together. This would mean that they are selected one at a time. So the code buss must be 8-bits. ( this is NOT a 16 bit processor, as much as the Z80 was a 16 bit processor )
I am sure this next week will bring many interesting discoveries. I will post here anything I find.