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RS-232 Pinout Quick Reference Card

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Pinout and COM Port Summary Card
EIA-232-E (RS-232)
Function
PIN #
DB-25 DB-9
EIA-530
Function
PIN #
DB-25
TO
DTE
TO
DCE
Shield 1   Shield 1    
Transmit Data (TD) 2 3
Transmit Data (A)
(B)
2
14
  >
Receive Data (RD) 3 2
Receive Data (A)
(B)
3
16
<  
Request To Send (RTS) 4 7
Request To Send (A)
(B)
4
19
  >
Clear To Send (CTS) 5 8
Clear To Send (A)
(B)
5
13
<  
DCE Ready (DSR) 6 6
DCE Ready (A)
(B)
6
22
<  
Signal Ground (SG) 7 5
Signal Ground (A)
7    
Received Line Signal Detector (DCD) 8 1
Received Line Signal Detector (A)
(B)
8
10
<  
DTE Ready (DTR) 20 4
DTE Ready (A)
(B)
20
23
  >
Ring Indicator 22 9 N/A     -----

 

SIGNAL
STATE
THRESHOLD VOLTAGES
Signal with Respect to SG Signal A with Respect to Signal B Signal A with Respect to Signal B
RS-232 RS-422 RS-485
"0", Asserted, ON, Space, Active +3 to +25 VDC +2 to +6 VDC (Transmitter)
+0.2 to +7 VDC (Receiver)
+1.5 to +6 VDC (Transmitter)
+0.2 to +12 VDC (Receiver)
"1", Disasserted, OFF, Mark, Inactive -3 to -25 VDC -2 to -6 VDC (Transmitter)
-0.2 to -7 VDC (Receiver)
-1.5 to -6 VDC (Transmitter)
-0.2 to -7 VDC (Receiver)
NOTE: Some RS-422 and RS-485 equipment use "+" and "-" descriptors.
The "-" corresponds to "A" and the "+" corresponds to "B".

 

Common AT Port Addresses and Interrupts
COM 1 3F8h IRQ4
COM 2 2F8h IRQ3
COM 3 3E8h IRQ4
COM 4 2E8h IRQ3
LPT1 378h IRQ7
LPT2 278h IRQ5
LPT3 3BCh  
Floppy Disk IRQ6
Real Time Clock IRQ8
Re-directed to IRQ2 IRQ9
Math Co-processor IRQ13
Hard Disk IRQ14

 

DECIMAL TO HEX TO ASCII CONVERTER

 

Decimal Hex ASCII conversion chartDecimal Hex ASCII Conversion Chart