Re: Char-ROM replacement

From: Rob Clarke <>
Date: Thu, 20 Sep 2012 19:46:20 +0200
Message-ID: <>
Do you have a USB programmer that will program 25xx's without an 
adapter? I'm trying to find a new one to replace my old RS232 DOS based 
one but I'm getting very confused my all the Willem look-a-likes....


On 20/09/2012 19:00, Gerrit Heitsch wrote:
> Hello,
> since I had a C64 char ROM (901225-01) go bad this year, I was looking 
> for a replacement. The pinout of the ROM matches the 2532 EPROM, but 
> the only one I had was 450ns and that's too slow. I tried it, but all 
> I got was a snow storm at power up.
> Then I found a few TMS2532-30 on ebay and got around to try 2 of them 
> today. Those are fast enough, you get the expected picture at power up.
> So, we have a verified drop-in replacement for the char ROM. The 2532 
> is NMOS so it will get warm, but you don't need any adapter, just 
> program it, and plug it into the socket.
> I also wanted to see how a ROM and the EPROM behave and used to the 
> scope to look at the time between _CS going LOW and the state change 
> on D0, showing me data being ready. The ROM did that in about 50ns! 
> The 2532-30 took about 150ns. Quite a bit faster than the expected 
> 300ns. Did TI just test for 300ns as highest speed back then and never 
> bothered to see if any were faster?
> Oh, and there is a 2532A too, available in 250ns, but needs a Vpp of 
> 21V instead of 25V. At least my programmer can't do that combination.
>  Gerrit
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Received on 2012-09-20 18:00:53

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