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2732 to 2532 adaptation
Posted: Tue Jul 16, 2019 2:43 pm
by albertusj
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.
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?
Re: 2732 to 2532 adaptation
Posted: Tue Jul 16, 2019 10:48 pm
by 1024MAK
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
Re: 2732 to 2532 adaptation
Posted: Wed Jul 17, 2019 7:22 am
by albertusj
I'll check the enable pin. Thanks
Re: 2732 to 2532 adaptation
Posted: Wed Jul 17, 2019 5:54 pm
by albertusj
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.
Is this correct?
Re: 2732 to 2532 adaptation
Posted: Wed Jul 17, 2019 7:21 pm
by 1024MAK
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
Re: 2732 to 2532 adaptation
Posted: Thu Jul 18, 2019 11:14 am
by albertusj
Thanks 1024!
Re: 2732 to 2532 adaptation
Posted: Tue Jul 23, 2019 3:37 pm
by rcade
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...
Re: 2732 to 2532 adaptation
Posted: Tue Jul 23, 2019 5:33 pm
by 1024MAK
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
Re: 2732 to 2532 adaptation
Posted: Tue Jul 23, 2019 5:46 pm
by rcade
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!