User`s manual

Remember that the Textool socket may have programming voltage
(Vpp) applied to various pins even during such commands as a List
command or Read command. Some algorithms on the 9000 use the
eprom “verify read” mode, which means that programming voltage
is applied during a “read” of the part. This will usually damage a part
such as a 2764A if you have the 2764 algorithm selected! Some
selections are always safe to use to just read a part if you are not
sure what selection to use. F27C64, F27C256 and 27512 are usually
safe (ON READS ONLY!).
You can use a 27512 selection to read any 28 pin part (including
ROMS). By noticing what locations within the address range have
duplicated data, or where data appears at all, you can usually deter-
mine what size the target part is. If you know where certain data is
supposed to appear, you can determine if it has masked chip select
lines.
PGMX Communications Diagnostics
Please refer also to the chapter on PGMX. PGMX can detect various
problems with the serial channel during communication. Error mes-
sages usually have a symptom and a diagnosis message, such as
“(beep) Framing Error (beep) Overrun error! Reduce baud rate”. Fol-
low the directions specified by the error message.
Persons using PGMX and making their own cable will most likely run
into the Framing error and the Overrun error. The cause of this is
usually they don’t have their CTS line on the 9000 hooked to the
DTR line on the computer. The computer can’t tell the 9000 to stop
sending. Stack errors are usually caused by the reverse, CTS on the
computer is not hooked to DTR on the programmer. The 9000 can’t
tell the computer to stop sending.
The second most frequent problem people run into is the fact they
can’t believe their computer can’t receive data at 57,600 baud. It
takes a fast computer (8 MHz AT or better) to handle data coming in
at that maximum rate. You will usually get framing errors or overrun
errors when this happens. The cure is to reduce the baud rate. Most
PC’s and XT’s (4.77 MHz) can handle data at 9,600 baud without
much difficulty.
Model 9000 Diagnostics Chapter 4
Page 19