2732 to 2532 adaptation

Discussions about Sinclair ZX80 and ZX81 Hardware
Post Reply
albertusj
Posts: 51
Joined: Sat Aug 18, 2012 12:44 am
Location: Somerset-West, South-Africa
Contact:

2732 to 2532 adaptation

Post by albertusj » Tue Jul 16, 2019 2:43 pm

Hi, I have a ZX80 built from a kit that currently uses a 2732 for the ROM. I'd like to test a 2532 I have on the board, but I'm not entirely clear on which pins need to be adapted.

Image
From Grant Searle's excellent site

Am I correct in stating that in order to adapt my board socket that is designed for a 2732 to accept a 2532, I need to swap the RED pins on the 2732 and 2532 and take Vpp to Vcc on the 2532?
ZX80/ZX81/ZX Spectrum

User avatar
1024MAK
Posts: 2414
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: 2732 to 2532 adaptation

Post by 1024MAK » Tue Jul 16, 2019 10:48 pm

On the board, which enable pin is actively used, pin 18 or pin 20 on the 2732? Or are both used?
Only, some ROM chips and the 2532 only have one enable pin.

And yes, the A11 line needs swapping.
Connect VPP to +5V.

Mark

albertusj
Posts: 51
Joined: Sat Aug 18, 2012 12:44 am
Location: Somerset-West, South-Africa
Contact:

Re: 2732 to 2532 adaptation

Post by albertusj » Wed Jul 17, 2019 7:22 am

I'll check the enable pin. Thanks
ZX80/ZX81/ZX Spectrum

albertusj
Posts: 51
Joined: Sat Aug 18, 2012 12:44 am
Location: Somerset-West, South-Africa
Contact:

Re: 2732 to 2532 adaptation

Post by albertusj » Wed Jul 17, 2019 5:54 pm

1024MAK wrote:
Tue Jul 16, 2019 10:48 pm
On the board, which enable pin is actively used, pin 18 or pin 20 on the 2732? Or are both used?
Only, some ROM chips and the 2532 only have one enable pin.

And yes, the A11 line needs swapping.
Connect VPP to +5V.

Mark
PIN 18 on 2732 is actively used. So what shall I do with GVpp on the 2732? It currently goes to A12. It looks like I'll just leave it since there's nowhere for it to go on the 2532.

Image

Is this correct?
ZX80/ZX81/ZX Spectrum

User avatar
1024MAK
Posts: 2414
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: 2732 to 2532 adaptation

Post by 1024MAK » Wed Jul 17, 2019 7:21 pm

Lift the VPP pin clear of the socket so it no longer makes contact with the socket. Then connect the VPP pin to +5V.

Connect A11 to A11. Connect /E to PD. As per your diagram above.

A12 being unconnected does not make any difference. All that will happen, is that the 4K bytes of the EPROM will appear between 0x0000 and 0x0FFF and then again between 0x1000 and 0x1FFF.

Mark

albertusj
Posts: 51
Joined: Sat Aug 18, 2012 12:44 am
Location: Somerset-West, South-Africa
Contact:

Re: 2732 to 2532 adaptation

Post by albertusj » Thu Jul 18, 2019 11:14 am

Thanks 1024!
ZX80/ZX81/ZX Spectrum

rcade
Posts: 18
Joined: Tue Dec 02, 2014 2:28 pm

Re: 2732 to 2532 adaptation

Post by rcade » Tue Jul 23, 2019 3:37 pm

I had to connect pin 18 to GND (pin 12) when I adapted a 2732A on my PET, or else the machine was unstable. It would work sometimes and not others, depending on whether the case was up or down. Very strange...

User avatar
1024MAK
Posts: 2414
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: 2732 to 2532 adaptation

Post by 1024MAK » Tue Jul 23, 2019 5:33 pm

rcade wrote:
Tue Jul 23, 2019 3:37 pm
I had to connect pin 18 to GND (pin 12) when I adapted a 2732A on my PET, or else the machine was unstable. It would work sometimes and not others, depending on whether the case was up or down. Very strange...
Yeah, if using a 2732 in place of a 2532, the unused control pin (be it /CE, /CS, /OE, /E or /G) has to either be tied to 0V/GND or to the other control pin.

Mark

rcade
Posts: 18
Joined: Tue Dec 02, 2014 2:28 pm

Re: 2732 to 2532 adaptation

Post by rcade » Tue Jul 23, 2019 5:46 pm

1024MAK wrote:
Tue Jul 23, 2019 5:33 pm
rcade wrote:
Tue Jul 23, 2019 3:37 pm
I had to connect pin 18 to GND (pin 12) when I adapted a 2732A on my PET, or else the machine was unstable. It would work sometimes and not others, depending on whether the case was up or down. Very strange...
Yeah, if using a 2732 in place of a 2532, the unused control pin (be it /CE, /CS, /OE, /E or /G) has to either be tied to 0V/GND or to the other control pin.

Mark
Ah, I see now the OP is going the other direction. Sorry for the confusion!

Post Reply