tlanders@sequent.UUCP (Troy Landers) (02/20/90)
I need help building a cable to connect a non-standard serial port on a
Tandy DMP-132 printer to the 9-pin serial port on an HP700/44 terminal.
Both have RS-232C serial ports, the Tandy's is just funny shaped
(a 4-pin DIN connector--made for the Tandy Color Computer). I am
having trouble getting them to "shake hands".
The pin charts for the two ports are as follows:
TANDY DMP-132
Port is set at 600 baud, 1 start bit, 8 data bits, no parity, and 2 stop
bits. (Baud rate is adjustable between 600, 1200, and 1400, everyting
else is fixed.)
Pin # rs232 Pin Name (Tandy's)
---- --------- --------------
1 - not used
2 DTR Status
3 SGND Ground
4 RXD Data
A word about pin 2: In the schematic, it is labeled DTR. The timing
chart shows that it is asserted when the printer is ready for data and
de-asserted when the printer is "busy".
HP700/44 Terminal
Port is set at 600 baud, 1 start bit, 8 data bits, no parity, and 2 stop
bits. (All settings are re-configurable.)
Pin # rs232 Pin Name (HPs)
---- --------- --------------
1 PGND Frame Ground
2 TXD Transmit Data
3 RXD Receive Data
4 RTS Request To Send
5 DTR Data Terminal Ready
6 DSR Data Set Ready
7 SGND Signal Ground
8 - not used
9 - not used
I have already tried the following configurations:
Printer Pin <--> Terminal Pin Result
----------- ------------ ------
DTR (pin 2) disconnected
SGND (pin 3) SGND (pin 7)
RXD (pin 4) RXD (pin 3) Absolutely Nothing
Printer Pin <--> Terminal Pin Result
----------- ------------ ------
DTR (pin 2) disconnected
SGND (pin 3) SGND (pin 7)
RXD (pin 4) TXD (pin 3) The correct characters came out
of the printer, but only if I
typed through VERY slowly. If
the printer received data too
fast (anything faster than my
typing), it "lost" the first half
of the line.
I suspect that the printer has a buffer which can only be written to
when the printer is not printing. When it receives a CR, it prints the
buffer, ignoring all in-comming data while it is printing, thereby
losing the first half of the line. The status pin (DTR, pin 3) must be
used to stop the in-comming data long enough for the printer to print
the data.
With this in mind, I set about connecting the printer's status pin
(DTR, pin 2) to the remaining pins to see if anything helped.
Nothing did. Since the HP700/44 does not carry the CTS pin on this
port, I wonder if this is the one I need.
Please help me to get these ports to shake hands. Thanks.
Please respond via email, I will post the responses.
Troy
-------------------------------------------------------------------------------
Troy Landers Sequent Computer Systems Inc.
UUCP: ...!sequent!tlanders 15450 S.W. Koll Parkway
Phone: (503) 626-5700 x4491 Beaverton, Oregon 97006-6063
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