TRS80 Laptop Connectors
Data on this page is from TRS-80 Model 100 Portable Computer Manual and it is available for educational purposes only.
RS232-C interface
1 GND Signal ground & Shield
2 TXR Transmit data
3 RXR Receive data
4 RTS Request to send
5 CTS Clear to send
6 DSR Data set ready
7 GND Signal ground
 8-19 NC Not connected
20 DTR Data terminal ready
21-25 NC Not connected

 
Parallel Printer Interface (Centronics)
 1 Strobe out Strobe Pulse
3,5,7,9
11,13,15,17
 PD0-PD7 out Data Bit (pdo=lsb)
19,23  NC   Not connected
21 BUSY in Busy signal to computer from prn
25 BUSY in Busy to computer from prn : high indicates device selected
 Even pins GND   Ground
26  NC   Not connected

 
Cassette Interface
1 Rem1 Remote Switch
2 GND Ground
3 Rem2 Remote Switch
4 RxC Receive data for CMT
5 TxC Transmit data for CMT
6 GND GND
7 NC Not connected
8 NC Not connected

 
Modem Interface
1 TL Conventional Telephone Unit
2 GND Logic GND
3 RxMD Direct connection to Tel Line (Ring)
4 RxMC Acoustic Coupler Connection (MIC)
5 TxMC Acoustic Coupler Connection (Speaker)
6 VDD
7 TxMD Direct Connection to Tel Line (Tip)
8 RP Ringing Pulse

 
Model-100 40 Pin External Bus SIgnal (RED=Active Low)
1 VDD 40 VDD
2 GND 39 GND
3 AD0 38 AD1
4 AD2 37 AD3
5 AD4 36 AD5
6 AD6 35 AD7
7 A8 34 A9
8 A10 33 A11
9 A12 32 A13
10 A14 31 A15
11 GND 30 GND
12 RD 29 WR
13 IO/M 28 S0
14 ALE 27 S1
15 CLK 26 CE for I/O Cont.
16 RD+WR 25 RESET out
17 INTA 24 INTA
18 GND 23 GND
19 RAM RAM RESET 22 NC
20 NC 21 NC
[Note: I suspect a few typos in the original in the table above. Refer to the following for signals that are common]
 
Model-102 40 Pin External Bus SIgnal (RED=Active Low)
1 VDD 2 VDD
3 GND 4 GND
5 AD0 6 AD1
7 AD2 8 AD3
9 AD4 10 AD5
11 AD6 12 AD7
13 A8 14 A9
15 A10 16 A11
17 A12 18 A13
19 A14 20 A15
21 GND 22 GND
23 RD 24 WR
25 IO/M 26 S0
27 ALE 28 S1
29 CLK 30 I/O controller select signal
31 E I/O MEM access enable signal 32 RESET out
33 INTRequest 34 INTAcknowledge
35 GND 36 GND
37 RAM RESET 38 NC
39 NC 40 NC
 
Bar Code Reader
1 NC Not connected
2 RxDB Receive data from bar code reader
3,4 NC Not connected
5 GND Ground
6 NC Not connected
7 GND Ground
8 NC Not connected
9 VDD +5V