Tag Archives: memory

PC-1500 28Kb – Part 2

This PC-1500 is more than an updated version with huge memory amount and double-speed oscillator.
It’s one of the firsts samples of the A04 production.

In this picture you can see the ROM version on the SC613128 IC.
Do you remember the A03 versions ? They have blue straps… like here on the display board :

And now lets see under the memory extension…
The board shows many blue straps like the A01 and A03 versions :

Sure this is a rare item for collectors.
It’s serial number is 20024876.

Who owns a such collector version ?
Take a screwdriver and verify your PC-1500s 🙂

Thanks again to Lukas ZELLER for this gift.

Many versions of PC-1500 ? PC-1600 too !

Hey, we focused on the PC-1500 and PC-2 versions but do you know the PC-1600 versions ?
As this pocket is compatible with PC-1500 we can talk about it.

I have two PC-1600 but they are not exactly same.
Lets see the old version :
PC-1600 V1

and the new one :
PC-1600 V2

The memory place is different, as small board for the V1 and on CPU board for the V2.
If you look at the Technical Reference Manual you will have the first version :
PC-1600SCH V1

And if you look at the Service Manual there is the V2 :
PC-1600SCH V2

Are you looking for a screwdriver to open your precious PC-1600 ? 😉

PC-1560 : CE-161 to replace system ROM ?

Working on the PC-1560 project need some tools.
We have to design a new system ROM but at this time don’t have to work with (E)EPROM programmers.
The best way is to look at our hardware stuff !

We most have CE-161, isn’t it ?
Ok, how does this memory module work ?
It need to be plugged on the 40 pins bus.
The PC-1500(A) schematics shows that we have these signals available on the connector:
– /Y0
– /Inhibit (active low to disable the system ROM)

CE-161 schematics shows a 40H138 (Demux) selected by /Y0 (active low) going to /G2A (active low). This signal is nothing but &0000H address.

The system ROM is at &E000H… /Y3 from the 40H139 in the PC-1500.
Simple, no ?

Ok, a DOUBLE hardware inverter is all we need.
The inverter will a the same time :
– connect 40H139 signal /Y0 or /Y3 to the CE-161 on /G2A
– connect /Inhibit to GND or let it to it’s high value.

The inverter must be inside the PC-1500.
Cut the strap from pin 4 of the 40H139.
Connect this pin to one side of the inverter.
Connect pin 7 to inverter’s other side.
Connecter inverter middle pin to the cutter strap.
Now you can choose CE-161 function : RAM or system ROM.
… don’t miss the /INHIBIT pin…

I will soon show your a picture of the system.

Here is the updated schematics.

CE-163 owners will have a dual ROM system… but be careful to switch ROM when powered off.