The PC-1500 is a really well designed pocket computer and offers many ways to extend it’s software and hardware capabilities.
Some companies were seduced by the Sharp solution and it’s “owner” memory modules.
EDTech was one of these companies and were offering a solution for education administrators : (Picture taken from eBay)
Externally it looks like the PC-1500A + CE-150.
But internally there is a custom memory module :
It holds a 57256 32KB EPROM
We have to distinguish three kinds of memory modules :
– RAMs stored between &0000 to &3FFF (like 4KB CE-151, 8KB CE-155, 8KB CE-159, 16KB CE-161 or 2x16KB CE-163)
– ROMs or EProms stored between &8000 to &BFFF (that extends the system with Basic instructions)
– Pseudo ROMs stored between &0000 to &3FFF (like the 7,8KB CE-160 used to store custom invisible Basic programs)
– EProms stored between &0000 to &3FFF used to store invisible Basic programs
The EDTech ROM is in this last case.
But if you understand address decoding “&0000 to &3FFF” is only 16KB wide.
On this module there is a TTL 74LS73 IC. It’s a dual J-K flip-flop with clear.
It’s function is to select one of the two 16KB pages.
Open the Technical Reference Manual and look for memory configuration and /S3 signal.
On the PC-1500 this signal select a memory zone starting at &5800.
On the PC-150A this signal select a memory zone starting at &6800.
Nice, this can work with the two pocket computers.
On my schematics you can see it connected to the CLK pin of the Flip-flop.
Now examine the content of each 16KB page (only the beginning, the rest is the EDTech program)… lines 11, 40 and 41
1st page :
2nd page :
The POKE instruction writes a value to a memory case. By this way the program can swap the page.
Depending on the address it writes a 0 or 1 on the J and K entries and the clock push it to the Q and /Q outputs.
It’s a very nice design, isn’t it ?
I asked EDTech to get some informations and maybe a user manual.
They answered but nobody was able to help me.
Can you ?
Contact me if you have other “non Sharp” modules… 😉
Building this website to remind the worldwide story of the Sharp PC-1500 is a crazy hobby. We are in 2015, 33 years after the first PC-1500, and lot of informations are going to disappear in the next years. All the people having worked on the PC-1500 projects, all the club members, all the resellers, all the users are from 50 to 80 years old. Some contacts told me “i have cleaned my house and don’t have anything left”, “all is gone to trash some years ago”… That’s very sad, isn’t it ?
A few months ago i have installed a statistic tool and each month i can see the really nice result of 3000 unique visitors and 7000 visits ! Do we need better proof that the PC-1500 is still popular in 2015 ? NO ! Thank you to all my readers ! Some comments on the articles or guestbook are welcome 😉
But some help is needed to save PC-1500 related items and papers before they go trash !
This is the role of my “Help needed” menu. It tell how you can help me and what i’m currently looking for.
Lukas told me about his gift that there will be a 28Kb PC-1500.
This was a good news !
But this is more than a good news.
Lets me present this updated machine.
Opening the CE-150 box shows us some nice things.
Do you see what i mean ? Examine this picture carefully…
First there is a sticker “28K”. This means that the memory size is 28Kb. It’s the maximum reachable on this pocket because of the display addressing method.
Let’s open the machine…
Here is it :
This extension it made of 13 x 6116 ICs and present a total amount of 26KB of memory.
It’s a very professional board. You can see where the RAM pins are placed ? Simply on the holes between sides. Well done guys !
This board is named “DF1SE PC 1503”. (If you know more about it then use the contact form to tell it to me.)
Second, there is a switch on the PC-1500 side :
Do you know why ?
The LH5801 microprocessor is driven by a 2,6Mhz oscillator.
In 1982 it was fast ! In 1984 it was slow ! lol
This button switch between the 2,6Mhz and a new 5Mhz oscillator. Yes, the twice !!!
Uh… this has some back effects to the real time clock… but the speed is here !
The printer case and the pocket pouch have being modified for the switch.
Third, there is a very nice update of the printer’s door.
A little black plastic strap help the opening.
Next time i will explain something very particular on this PC-1500.
Do you have an idea ???
Do you know the Sharp and Tandy Service Manuals ?
Here are they, modified to have one PDF file (OCR) per item.
All manuals are scanned from my own materials.
If you have some of the missing manuals (or not in this list) to offer (or sell) please tell me.
If you download something, please feel free to write a little comment.
Yes, you have correctly read the title !
I have informations about the unfindable PC-1500 extension : the CE-165W !
Many of us have long sought this device without finding anything.
But luckily a friend had a few pages stapled, lost in a pile of documents.
What is the CE-165 W ?
This is not an EPROM programmer.
I guess you are disappointed …
But it is actually a programmer for the CE-160 modules.
It can program 16 once.
The verification phase is done by module.