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I have a Marpet MP605 clock module: http://amigakit.leamancomputing.com/...roducts_id=595
It must be used together with a MP604A memory expansion: http://amiga.resource.cx/exp/marpet604
I do not have such a RAM expansion. So I wondered if this clock module can be modified to work with
any other memory expansion for the A600 (or A1200).
Not the module itself - it's the other RAM board that will need the modification.Quote:
Originally Posted by leof
From a quick look at the module and the Marpet RAM board, it seems that the Marpet RAM board doesn't have any partial circuitry for the RTC module and simply acts as a pass-through for the RTC-related signals present on the trapdoor connector.
The complete RTC circuitry seems to be present on the module.
Therefore you simply need to feed it the RTC-signals, and of course Vcc and GND. Take a look at the schematics for the A600 to see what is what on the expansion connector, then solder wires to the appropriate contact points on your RAM board and route them to the RTC module.
You'll need schematics for the RTC too - namely the A601 schematics (but I bet the A501 schematics will do just as well).
Thanks! Appreciate your help.
I found some schematics: the first one is from the A600 memory expansion bus and the second is taken from the A501.
Attachment 84092 Attachment 84091
I don't yet see the connections between these two. Can you assist?
See the photo of the OKI chip diagram. Use the A501 schematic to match the OKI pins to the connections on the 2x7 module connector.
Since there are 14 pins there, they must be: 4 + 4 for address + data on the OKI chip, three lines for read, write, select on the OKI chip (= total 11 lines so far) and +5V, +12V and GND (another 3 lines, total 14).
So it's logical to assume that the 14 connections on the 2x7 module connector match the above.
Use continuity test to match the 2x7 connector pins to the RTC pins.
As per naming, on the P6 A600 trapdoor connector the correspondence should be:
A501 RTC name ----- A600 P9 trapdoor connector name
XD 0-1-2-3 (OKI pins 14-13-12-11) ---- D 0-1-2-3
XA 2-3-4-5 (OKI pins 4-5-6-7) ---- A 2-3-4-5
_XCLKRD (OKI pin 8 ) ---- _IORD
_XCLKWR (OKI pin 10) ---- _IOWR
_XCLKCS (OKI pin 2) ---- _RTC_CS
Pin 9 of the OKI chip is ground
Pin 18 of the OKI chip is power (+5V)
The common end of the two diodes should be connected to +12V through a resistor (supposedly the resistor seen on the RTC module).
Wow! That's great!
I will need some time to study and perform this. Will provide feedback how it goes.
Many thanks!
You're welcome.
To make things easier, first make a correspondence table between the 14 contacts on the 2x7 connector and the 11 OKI pins + 5V + 12V + GND (use the OKI schematic and the multimetre to determine the correspondence), i.e.
2x7 pin --- OKI pin# or 5V/12V/GND
1 - ?
2 - ?
...
13 - ?
14 - ?
Once you've filled the 2nd column with the correct values, insert a 3rd column and use the correspondence table I wrote to match OKI pins to P9 names.
And finally insert a 4th column where you'll write next to the P9 names the relevant P9 pin#, based on the P9 connector schematic.
Then you can ignore the inner columns - the 1st and 4th columns will directly provide you with the correct matching between the contacts on the 2x7 module connector and the A600 P9 connector pins.
Good luck!
Thanks again!
I have several memory expansions one of which is http://amiga.resource.cx/exp/baseboard601
Description says it even has a battery backed up clock! The PCB seems to have the circuitry, but no components.
Would it be easier to move parts from the clock module to the expansionboard?
Attachment 84139
Maybe (see photo). You'll need an extra diode and to not damage the oscillator while desoldering. But on some photos of the RTC version of the card, the oscillator is not installed, I don't know what's with that.
Where is the battery supposed to go?
Blue double arrow. It's where the OKI chip should be. Of course the battery will be installed on the other side of the PCB.