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Author Topic: Internal RTC and 512KB Flash-ROM for Saint's memory expansions (Read 2954 times)

Online gflorez

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In the past, with the aid of Zozo, I build a RTC that took advantage of an unused header of the Microteam Exdos clone card. He has modified his Zozotools to work with it, but is an approach that only serves to that Exdos clone card.

Now I will try an internal RTC with the aid of Zozo and Pear. I think it will work exactly like the Meszaros' Clock card, because it will use the same Z80 ports. It would be adapted to all Enterprise computers, because I will take the signals from the internal memory expansion headers, that the 64 also have.

Only three signals must be taken from other points at the EP main-board, /IORQ, /M1 and /RESET, the last not used on Meszaros' project. This is because I am following the schematics provided by Pear, that substitutes some logic gates by a GAL and includes that /RESET signal.

The RTC chip is the same that I used with the Microteam, the Dallas DS12C887, totally compatible with the original chip mounted on the Clock card, the Motorola MC146818, but with the added bonus of  being CMos, to have static Ram, crystal and  a battery included on the same package. This saves a lot of circuitry, compared with the original chip.

My card, made of strip-board, will measure about 60x50 mm, little enough to fit inside of all EPs. I will put here the details.
« Last Edit: 2017.February.03. 10:41:34 by gflorez »

Online gflorez

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Re: Internal Real Time Clock
« Reply #1 on: 2017.January.01. 13:08:41 »
Some advances, all the leads and jump wires soldered.
« Last Edit: 2017.January.01. 13:12:03 by gflorez »

Online gflorez

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Re: Internal Real Time Clock
« Reply #2 on: 2017.January.02. 13:46:25 »
Stripes cut.
« Last Edit: 2017.January.02. 17:32:26 by gflorez »

Online gflorez

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Re: Internal Real Time Clock
« Reply #3 on: 2017.January.22. 21:33:52 »
I am still waiting for a cheap Chinese chip programmer able to burn the ATF20V10...

-----------------

In the meantime....

If I get the RTC working on my Ep, it will need Zozotools to show the clock on the screen. The ZT19UK.ROM weights 32KB, and I have no spare space on the internal ROM nor in the SD-reader cartridge. The easy way would be to put it on the EXDOS Rom socket, but actually I don't have my Microteam card with me.

I have thought on adding a 512KB  Flash-ROM to the installed 1MB Saint's memory expansion. The second 512KB SRAM chip is mounted piggyback on the first, so I think that there isn't enough space on the upper side of the little card, but plenty on the underside above the Nick chip. The Flash-ROM chip has almost the same pin-out than the used SRAM chips, then I can solder the chip to the underside contacts. There are only 4 contacts out of the 32 that must be moved.

For the address decoding I will use the same GAL16V8 used for the SRAM, on one of its unused pins.  The Flash-ROM will go on the same memory address area than the 512KB DRAM of the Microteam, because it will be disabled due to compatibility problems with the 10MHz mode.

But again I need the chip programmer to change the content of the GAL chip.
« Last Edit: 2017.January.23. 15:41:21 by gflorez »

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Re: Internal Real Time Clock
« Reply #4 on: 2017.January.25. 23:15:09 »
There are three signals not present on the internal expansion headers but needed by the Real Time Clock: /M1, /IORQ and /RESET.

I have found spots to solder them on the zone near the external expansion connector:




Edit: I have corrected an error on the drawing. /IORQ is B3 on the external connector, not B2.
« Last Edit: 2017.January.26. 13:13:38 by gflorez »

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Re: Internal Real Time Clock
« Reply #5 on: 2017.February.03. 10:33:39 »
The 512KB Flash-ROM arrived. Still waiting for the chip programmer.

Online gflorez

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #6 on: 2017.February.09. 12:20:19 »
The programmer arrived, and some newbie problems solved.

This is for pear:

The eight of the clock chip, DS12C887+, is exactly 8mm, the same as the two memory chips soldered piggyback.

Once connected on its header, Saint's card+chips raise upto 20mm.

Sorry for the dirt in my fingers... my job is car repairing....
« Last Edit: 2017.February.09. 12:32:36 by gflorez »

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #7 on: 2017.February.09. 14:23:10 »
The two memory expansions compared.

Online gflorez

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #8 on: 2017.February.09. 17:13:42 »
Now I have programmed the 512 Flash with all sort of Roms, in boundaries of 64KB, for easy upgrade.

This is the look of the chip soldered under Saints's board.

Online gflorez

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #9 on: 2017.February.09. 17:29:00 »
The board in its place. The pins of the chip are three or four mm away of the nearest object.

Online geco

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #10 on: 2017.February.09. 18:30:02 »
Looks good :)
Are you still able to put the top of EP into it's place? :)

Offline Zozosoft

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #11 on: 2017.February.09. 18:31:58 »
This is the look of the chip soldered under Saints's board.
All pins connected? If I remember right, some pins ar different at the SRAM and Flash ROM!

Online gflorez

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #12 on: 2017.February.09. 19:37:19 »
Looks good :)
Are you still able to put the top of EP into it's place? :)

The piggyback soldered chips where originally put by Saint. They fit...

All pins connected? If I remember right, some pins are different at the SRAM and Flash ROM!

Thanks Zozo, I remember well your tutorial about ROMS and SRAM.

Only two pins soldered to see all in place. Now I will proceed to solder the rest rotating the needed pins.


Online gflorez

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #13 on: 2017.February.10. 10:52:12 »
Pear is making some measurements with the internal expansion headers.

This picture is to show how the second header is placed under the narrowing in the upper housing at the external expansion port. The red line marks the limit of the narrowing, about 7 mm over the main board.

Offline pear

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Re: Internal RTC and 512KB Flash-ROM for Saint's memory expansions
« Reply #14 on: 2017.February.10. 11:01:57 »
Thanks :)
Very tight. Badly designed :(