HP 7470A Interfacing And Programming Manual page 153

Minimum Interface Connector Pin Allocations
Pin No. RS-232-C CCITT V.24 Function/ Signal Level
2 BA 103 Data line from plotter
(TDATA) High = ON = "0" = +12 V
= SPACE
Low = OFF = "1"= —12V
= MARK
3 BB 104 Data line to plotter
(RDATA) High = ON = "O"= +3 V
to +25 V
Low = OFF = "1"= -3 V
to -25 V
7 AB 102 Signal ground (Return
(SGND) line)
In addition to the minimum requirements for communication, six more
lines are connected as shown in the following table. These lines are
required to implement full duplex communication, intermediate baud
rate, hardwired handshake mode, and monitor mode. All remaining
pins make no internal connection.
Pins 14 and 16 are wired in the special Y-cable, available as Option 16,
to implement monitor mode. The Y-cable schematic is shown below.
NOTE: Hardwire handshake cannot be used to prevent buffer overflow
when the Y-cable is connected. This is because pin 20 is connected
between the COMPUTER and TERMINAL c onnectors, but not to the PLOTTER
connector. I
COMPUTER 3 2 7 1 4 5 6 8 25
16
14
I
I
I
I
1 |
I
I
I
-1­
KJ
PLOTTER
TERMINAL 3 2 7 1 4 5 6 8 25
PINS 4, 5, 6, AND 8 THROUGH 25 ARE DIRECTLY CONNECTED BETWEEN THE
COMPUTER AND TERMINAL CONNECTORS.
Y-cable Schematic
RS-232-C/CCITT V.24INTERFACING 10-11