z80 CPU on Corcomp Triple-Tech Card

[+retroclouds]

There’s currently a Triple-Tech Card up for sale on Ebay and there’s a nice picture with lots of details.

https://www.ebay.de/itm/Ti-99-4a-Corcomp-Triple-Tech-card-for-PEB-box/254613797358

 

Looking more closely I notice they sneaked a Zilog Z80 CPU on there. What is it used for?

 

I mean the only thing the card does is:

• Host a speech synthesizer board
• Clock
• RS232 64k printer buffer

 

Did I miss something? Is having a Z80 on there total overkill?

Well there will be no danged Z80 in my PEB (unless perhaps me running some emulated Z80 on the raspberry in my TIPI PEB board) ?

Edited June 6, 2020 by retroclouds
changed RS232 to 64k printer buffer

[speccery]

Interesting picture. Since I don't have a PEB, I am always learning about new things that were designed for the PEB. And continue to be intrigued by these. As I know nothing about the board, I guess I can make completely random comments: it appears the Z80 could be controlling a printer buffer. There is 64K RAM on board. Looking at the PCB design it would be interesting to be able to read what chip U5 is, as it seems to sit between the Z80 computer and TI's bus. Looks like they basically slammed a full CP/M computer on board

[+jedimatt42]

before microcomputers, these same cpus were microcontrollers. This is a perfect little job for a Z80... 

 

These things were pretty isolated if I recall... The z80 is reading from one parallel connector, and loading it into memory, and feeding things out the other port. control isn't done through the 9900... the 2 buttons on the back clear the buffer and reprint or something like that... There is no reason given the function of the board for it to do anything more than take power from the peb. 

 

Now, you could probably replace that eprom with an operating system, such as CP/M, with IO routines modified to interact over parallel with a program running on the 4A, using the 4A's parallel port, and multiplex screen, keyboard, and disk through that... like a parallel version of the morning-star except maybe the morning-star had direct disk access... 

[apersson850]

I don't have any Triple-Tech card, but I did use one for a little while. I borrowed it from a friend, in order to write a driver for the p-system, so the real time clock on the Triple-Tech card could be used to set the date in the p-system automatically. Unlike the standard operating system in the TI, the p-system tags all files with creation dates. Normally, you have to set the date manually, but if you have a real time clock in the system, you can write some code in the p-systems *SYSTEM.STARTUP file to set the date automatically.

 

You're right about the purpose of the Z80 CPU. It isn't connected to the PEB address or data bus lines, but lives a life on its own, up in the corner of the card, as a print spooler.

Edited June 5, 2020 by apersson850

[Omega-TI]

8 hours ago, retroclouds said:

Well there will be no danged Z80 in my PEB (unless perhaps me running some emulated Z80 on the raspberry in my TIPI PEB board) ?

Well, that chip is for the printer buffer portion of the card, so if you do not need the printing capabilities of the card, it runs just fine as a "Double Tech Card" with the Z-80 removed.

 

<< CLICK ON IMAGE FOR ENLARGED VIEW >>

[+dhe]

I always thought the DSR would be interesting, because somewhere in the 9900 code, must be the z80 code....

[+jedimatt42]

3 hours ago, dhe said:

I always thought the DSR would be interesting, because somewhere in the 9900 code, must be the z80 code....

That's someone interesting... does the Z80 share the EPROM, with the Z80 on hold while the 4A accesses the EPROM, or on powerup, does the 4A copy the tiny print buffer code into the Z80's RAM... 

 

The EPROM would answer that... 

[+OLD CS1]

4 hours ago, dhe said:

I always thought the DSR would be interesting, because somewhere in the 9900 code, must be the z80 code....

I seriously doubt it.  I suspect the printer buffer is an isolated system, much like the printer adapters for the Commodores.  The CPU just continually watches the input port, caches what it receives, and spools it out.  As a bonus it monitors the buttons to perform re-print or buffer clear.

[+jedimatt42]

There appears to only be one EPROM on the board, so while the Z80 code should be punitively puny, I think it would be interesting to understand how the EPROM is shared.  It could also be as simple as a 16k eprom, with one address line selecting the TI side vs the Z80 side.   That might be the simplest way to solve the problem... just put the Z80 on hold while the TI page of the EPROM is selected. 

[+OLD CS1]

Nah, mate... two ROMs.  One below the Z80 and one below the battery.  Attached is a better view.  I am hoping to have one in my hands soon enough, should it be allowed.

[+jedimatt42]

Ah from the earlier picture I assumed that was some old fat clock chip... I see the clock over by the tuning device. 

 

Yep, so only relation to the 4A is power. It is appropriately named, just 3 completely separate devices sharing some fiberglass.

[BillG]

The Z80 is performing an essential function - refreshing the DRAM...

[apersson850]

The picture where the Z80 has been removed has two Hitachi static RAM chips instead of PROM on the board. Or in the sockets, actually.

[+OLD CS1]

There do not appear to be any data lines between the Z80 and TI-99 sides of the Triple-Tech. There are some spurious lines here and there, but nothing which looks like a data buss.  I am going to get a dump of the DSR and Z80 ROMs.

 

Can anyone tell me what the value of R12 (upper-right corner of the board by the Z80) is?  This one is burned.  It appears to feed the resistor pack RP3.