Serial Cable for Old HP-48G Series
Connect your HP-48GX, HP-48G+, HP-48G, HP-48SX, or HP-48S to your computer with this high quality 9 pin (PC) to 4 pin (Calc) serial cable. This cable is not suitable for any other calculators except those listed above.
Looking at back of HP-48:
---------
| 1 2 3 4 |
\_______/
Here are the pinouts for the HP-48G serial port:
4 3 2 1
/------------|-|-|-|----\
| 48SX | Pin Function Standard RS232 pin eqv.
| ___________________ | (25 pin connector)
| | | | 1 Chassis Ground 1
| | 4: "THIS" | | 2 Transmit Data 2
| | 3: "IS" | | 3 Receive Data 3
| | 2: "THE" | | 4 Signal Ground 7
| | 1: "SCREEN" | |
| ------------------- |
| |
| [A] [B] [C] [D] [E] [F] |
| MTH PRG CST VAR ^ NXT |
| . . . . . . |
If you're making a cable, just make a standard null modem cable.
(reverse RX and TX)
HP-48 pin RS232 pin
CHG 1 - - - - - - - - 1 CHG Chassis ground does not
actually have to be connected.
TX 2 ------\ /------ 2 TX
X
RX 3 ------/ \------ 3 RX
GND 4 --------------- 7 GND



