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Author Topic: Real Time Clock on a Microteam EXDOS (Read 10156 times)

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #15 on: 2014.February.14. 00:58:01 »
And powering with only 5vcc. With accumulator or battery.

Sorry, the picture was taken with the Android snapshot.(pressing volume down + power)
« Last Edit: 2014.February.14. 01:03:45 by gflorez »

Offline Zozosoft

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Re: Real Time Clock on a Microteam EXDOS
« Reply #16 on: 2014.February.16. 19:19:39 »
Dallas DS1287 compatible with the originally used MC146818, but including all subcircuits!
I think it is need just wiring for the MICROTEAM card expansion port!

It looks the current part number is a DS12887/DS12C887.
« Last Edit: 2014.February.17. 09:30:48 by szipucsu »

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #17 on: 2014.February.16. 23:09:04 »
OH! thanks. Then  I will equivocate less ...


Only the decoder part is now necessary. So, I can follow the original design. The resonator¿?(CD4069U) of the crystal was the part I found more difficult to understand. There are easier approaches on the Web.


Thanks again, Zozo.

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #18 on: 2014.February.17. 20:41:35 »
I have a doubt about -CS as, in the original scheme is only active(-) if the two voltages (+9 v and +5 v) are present. But I have read in the data sheet of the MC146818 it must(can) be set permanently to  0v if not used.
-------------------------
Tengo alguna duda con -CS, que en el esquema original solo esta activo(-) si están presentes los dos voltajes(+9v y +5v). Pero he visto en el informe del MC146818 que se debe(puede) dejar permanentemente a 0v si no se usa.

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #19 on: 2014.February.17. 22:33:02 »
On  the other side, -CS is ignored with voltage lower than 4,25 .

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #20 on: 2014.February.18. 01:05:49 »
It seems to me that the little 13+13 connector on the Microteam EXDOS card is for another WD177X and so  to manage two more floppies.

It lacks the necessary A3 to A7(*) address lines, or a -WR signal, but there are  nine pins  that can be modified to suit.

B6, B7, B8, B9, B10, A6, A7, A10 and A11
--------------------
Me parece que el pequeño conector de 13+13 de la tarjeta EXDOS Microteam es para otro WD177X y por lo tanto para gobernar dos floppies mas.

Carece de las lineas de direccion necesarias A3 a A7(*), o de la señal -WR, pero hay nueve pines que pueden ser modificados para esas funciones.

B6, B7, B8, B9, B10, A6, A7, A10, y A11.

* Edit: addresses A2 to A7
« Last Edit: 2014.February.18. 11:04:16 by gflorez »

Offline Zozosoft

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Re: Real Time Clock on a Microteam EXDOS
« Reply #21 on: 2014.February.18. 09:34:58 »
Quote from: gflorez
It seems to me that the little 13+13 connector on the Microteam EXDOS card is for another WD177X
No, it is used for EPROM programmer, SIO or PIO interface, etc

Quote
and so  to manage two more floppies.
The EXDOS (with original Shugart pinout) can handle four drives. Only the PC pinout limit to two drives, but you can add one Shugart standard drive as third to two PC drives.

Quote
It lacks the necessary A3 to A7 address lines
Not too important for simple devices as the RTC chip.

Quote
, or a -WR signal
It is as combined predecoded signals.

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #22 on: 2014.February.18. 10:41:05 »
No, I'm not interested in more floppies, only want to follow strictly the original Mészáros design so not force you to modify your ZTools.

But....... If that means easy work for you.... can you guide me on how I can select, write and read the chip so that your program can interact with it?


The WD177X is accessed with only two address lines, we can do the same. And the -WR can be substituted with  a spare negative output from the IC10 or IC11 of the Microteam EXDOS card, the "unwanted" pin signals that I mentioned earlier.  But then is necessary you can access the signal via software to interact with the RTC.



I don't understand fully electronics(nor deep programming), only a little electricity and logic, so I would need you to specify which signals are more appropriate to access the clock.



Specifying, in Mészáros design U1 and U5B, you can put the address lines not present (A2-A7) to 5v and "nothing" will change?
« Last Edit: 2014.February.18. 10:51:12 by gflorez »

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #23 on: 2014.March.03. 13:32:09 »
Before I send you the Microteam card, I would like also send you the prototype of RTC to try if it works and then you can adapt your Zozotools.


As we only have A0 and A1 on the Microteam expansion connector, and to follow close the original Mészáros design, what do you think of changing the 74ls30(U4) with a 74LS10(three input nand gate)?


And, what if we substitute -WR by -P38 or -P30 (m or l) coming from IC10B (Microteam)?

But I still don't have A7.

I don't know if the clock can be accessed then.
« Last Edit: 2014.March.03. 19:16:23 by gflorez »

Offline Zozosoft

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Re: Real Time Clock on a Microteam EXDOS
« Reply #24 on: 2014.March.07. 11:48:10 »
Now I find some time for study how work the clock board:
U5B and A4 do full decode for I/O address access at ports 7Eh,7Fh
A1-A6 needed to be 1, A7 0, IORQ 0, and M1 also 1. M1 is important, because the IORQ active at Interupt accept cycle with M1. Non active M1 can identify the valid I/O operations. (Not using the M1 are the one of the bugs in the Spectrum Emulator card original version.)

U5A and U5C&D decode the port signal to separate AS and DS signals for the RTC chip.
AS will be 1 when port 7Eh accessed, DS will be 1 when 7Fh accessed.

On the MICROTEAM EXDOS card we have a predecoded signals:
Valid I/O siganal decoded with M1 and IORQ:
NW1A: 1Ah write
NO1B: 1Bh write
X19: 19h read
Y1A: 1Ah read
NI1B: 1Bh read
Just address decoded, these need additional decoding with IORQ and M1
P30: 30-37h
P38: 38-3Fh
All are active low.

For the RTC I think the best way use a XOR gates (74LS86 or compatibles) for combine the 1Ah read/write as AS, and 1Bh read/write as DS
One gate for NW1A and Y1A, if one (and only one) of them 0 then the output will be 1 as the RTC need it.
Another gate for NO1B and NI1B.

Third gate used for invert the RD signal for the RTC:
One pin the RD, another to +5V then the output are inverted go to the RTC RW pin.

When using the Dallas chip, then connect CS just to GND. It is internally disabled when no VCC.
« Last Edit: 2014.March.07. 12:14:44 by Zozosoft »

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #25 on: 2014.March.07. 16:45:11 »
Thanks for the information. That simplifies the project some more...

Then the U3 74LS245 is no more needed, is it?

Offline Zozosoft

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Re: Real Time Clock on a Microteam EXDOS
« Reply #26 on: 2014.March.07. 16:54:12 »
Yes it is not needed, same present on the MICROTEAM card (near to the edge connector).

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #27 on: 2014.March.07. 18:18:35 »
Then -M1 and A0-A7 doesn't needed?

Do you say something like this?:



Edit: the pins of the third gate now are correctly connected...
« Last Edit: 2014.March.10. 15:11:40 by gflorez »

Offline Zozosoft

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Re: Real Time Clock on a Microteam EXDOS
« Reply #28 on: 2014.March.07. 18:23:27 »
Quote from: gflorez
Then -M1 doesn't needed?
We use signals which are predecoded with M1. (The others (P30/P38) need a M1 and IORQ decoding)

Quote
Do you say something like this?:
Yes.

Offline gflorez

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Re: Real Time Clock on a Microteam EXDOS
« Reply #29 on: 2014.March.07. 18:35:57 »
Sorry, I edited after you reply.

And A0-A7 is no more needed?