Getting Started with GCC-ERC32: C/C++ Compilation System for Mission Critical Spacecraft Applications
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D.2. RS-232 Information

The wiring of a null modem cable is given in Table D-3.

Table D-3. Null Modem Wiring and Pin Connection

 25 Pin9 Pin 9 Pin25 Pin 
FG (Frame Ground)1N/A----------N/A1FG
TD (Transmit Data)23----------23RD
RD (Receive Data)32----------32TD
RTS (Request To Send)47----------85CTS
CTS (Clear To Send)58----------74RTS
SG (Signal Ground)75----------57SG
DSR (Data Set Ready)66----------420DTR
DTR (Data Terminal Ready)204----------66DSR

The RS-232 standard is given in Table D-4.

Table D-4. The RS-232 Standard

DB-25DCEDB-9   
1  AAxProtective Ground
2TXD3BAITransmitted Data
3RXD2BBOReceived Data
4RTS7CAIRequest To Send
5CTS8CBOClear To Send
6DSR6CCOData Set Ready
7GND5ABxSignal Ground
8CD1CFOReceived Line Signal Detector
9  --xReserved for data set testing
10  --xReserved for data set testing
11   xUnassigned
12SCF  OSecndry Rcvd Line Signl Detctr
13SCB  OSecondary Clear to Send
14SBA  ISecondary Transmitted Data
15DB  OTransmisn Signl Elemnt Timng
16SBB  OSecondary Received Data
17DD  OReceiver Signal Element Timing
18   xUnassigned
19SCA  ISecondary Request to Send
20DTR4CDIData Terminal Ready
21CG  OSignal Quality Detector
22 9CEORing Indicator
23CH/CI  I/OData Signal Rate Selector
24DA  ITransmit Signal Element Timing
25   xUnassigned
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