Needham SA-20 Eprom Programmer
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Needham's SA-20 EPROM Programmer

RS232 Cable - New Cable, New Problems
I was really hoping a $7 cable would solve all my problems, but after hooking things up and spending about an hour trying to get the cable to work, it wasn't even connecting to the SA-20.  I matched the port baud rates, parity, etc... I tried just about everything under the sun.  With the UserPort software, without the software.  By the end, I was so tired of fighting with the programmer, I was on the MCUMall site about to order the True USB GQ-4X and be done with it.  But after reading the forum and seeing that 2532 and 2532A eproms are considered (TEST) and some people have had issues with certain chips, I decided to try the serial cable one last time..

During my last-ditch effort, I decided I should verify the pinout on the serial null modem cable.  Somehow I had a feeling that no matter what I bought I'd end up with the wrong cable.  But a null modem serial cable's supposed to be just that!  Checked continuity of pins from db9 to db25 with my multimeter and low and behold, the wiring's wrong!  I don't know how many types of db9 to db25 null modem wirings there are, but definitely more than one.  So the cable I got was a non-standard wiring.

Not one to give up easily I cut the serial cable in half and stripped all the tiny wires and began figuring out how the wires corresponded to the pins.  Twisted and soldered them together so that the pinout would match a standard null modem cable pinout.

Here's what the pinout should look like:

Signal Name DB-9 Pin DB-25 Pin  
FG (Frame Ground) - 1 FG
TD (Transmit Data) 2 3 RD
RD (Receive Data) 3 2 TD
RTS (Request To Send) 8 5 CTS
CTS (Clear To Send) 7 4 RTS
SG (Signal Ground) 5 7 SG
DSR (Data Set Ready) 4 20 DTR
CD (Carrier Detect) 4 20 DTR
DTR (Data Terminal Ready) 1 8 CD
DTR (Data Terminal Ready) 6 6 DSR


After this, I again tried to connect with the SA-20 using the serial cable and...... no go.  Great, more time invested in something that doesn't work!  But then I remembered I had changed a few serial port settings in Device Manager, and changed them back.  Being used to failure with this programmer, I wasn't expecting much -- but to my astonishment it FINALLY connected to the software!!

But will file transfers to the SA-20 now work?  Let's see..

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