IBM PC Serial Card with a 25-pin connector (obsolete 8-bit ISA card) | A PCI Express ×1 card with one serial port | A four-port serial (RS-232) PCI Express ×1 expansion card with an octopus cable that breaks the card's DC-37 connector into four standard DE-9 connectors | A converter from USB to an RS-232 compatible serial port; more than a physical transition, it requires a driver in the host system software and a built-in processor to emulate the functions of the IBM XT compatible serial port hardware. |
9-pin to 25-pin D-type adapter cable | Pair of femaleMini DIN-8 connectors used for RS-422 serial ports on a Macintosh LC computer | A Hirose 3560-16S used for RS-232 on a Tatung TWN-5213 CU tablet computer. Below is a mating 3540-16P-CV connector. |
Signal | Direction | Connector pin | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Name | V.24 [de] circuit | Abbreviation | DTE | DCE | DB-25 | DE-9 (TIA-574) | MMJ | 8P8C ('RJ45') | 10P10C ('RJ50') | ||||||
EIA/TIA-561 | Yost (DTE) | Yost (DCE) | Cyclades[6] | Digi (ALTPIN option)[7] | National Instruments[8] | Cyclades[6] | Digi[9] | ||||||||
Transmitted Data | 103 | TxD | Out | In | 2 | 3 | 2 | 6 | 6 | 3 | 3 | 4 | 8 | 4 | 5 |
Received Data | 104 | RxD | In | Out | 3 | 2 | 5 | 5 | 3 | 6 | 6 | 5 | 9 | 7 | 6 |
Data Terminal Ready | 108/2 | DTR | Out | In | 20 | 4 | 1 | 3 | 7 | 2 | 2 | 8 | 7 | 3 | 9 |
Data Carrier Detect | 109 | DCD | In | Out | 8 | 1 | N/A | 2 | 2 | 7 | 7 | 1 | 10 | 8 | 10 |
Data Set Ready | 107 | DSR | In | Out | 6 | 6 | 6 | 1 | N/A | 8 | N/A | 5 | 9 | 2 | |
Ring Indicator | 125 | RI | In | Out | 22 | 9 | N/A | N/A | N/A | N/A | N/A | 2 | 10 | 1 | |
Request To Send | 105 | RTS | Out | In | 4 | 7 | N/A | 8 | 8 | 1 | 1 | 2 | 4 | 2 | 3 |
Clear To Send | 106 | CTS | In | Out | 5 | 8 | N/A | 7 | 1 | 8 | 5 | 7 | 3 | 6 | 8 |
Signal Ground | 102 | G | Common | 7 | 5 | 3, 4 | 4 | 4, 5 | 4, 5 | 4 | 6 | 6 | 5 | 7 | |
Protective Ground | 101 | PG | Common | 1 | N/A | N/A | N/A | N/A | N/A | N/A | 3 | N/A | 1 | 4 |
Bit rate (Baud rate) | Time per bit | Windows predefined serial port speed[19][20] | Other reasons that this speed is common |
---|---|---|---|
50 bit/s | 20000 μs | No | Listed in PC16550D datasheet[21] |
75 bit/s | 13333.3 μs | Yes | |
110 bit/s | 9090.9 μs | Yes | Bell 101 modem |
134.5 bit/s | 7434.9 μs | Yes | |
150 bit/s | 6666.6 μs | Yes | |
300 bit/s | 3333.3 μs | Yes | Bell 103 modem or V.21 |
600 bit/s | 1666.7 μs | Yes | |
1,200 bit/s | 833.3 μs | Yes | Bell 202, Bell 212A, or V.22 modem |
1,800 bit/s | 555.6 μs | Yes | |
2,400 bit/s | 416.7 μs | Yes | V.22bis modem |
4,800 bit/s | 208.3 μs | Yes | V.27ter modem |
7,200 bit/s | 138.9 μs | Yes | |
9,600 bit/s | 104.2 μs | Yes | V.32 modem |
14,400 bit/s | 69.4 μs | Yes | V.32bis modem |
19,200 bit/s | 52.1 μs | Yes | |
31,250 bit/s | 32 μs | No | MIDI port |
38,400 bit/s | 26.0 μs | Yes | |
56,000 bit/s | 17.9 μs | Yes | V.90/V.92 modem |
57,600 bit/s | 17.4 μs | Yes | V.32bis modem with V.42bis compression |
76,800 bit/s | 13.0 μs | No | BACnet MS/TP networks[22] |
115,200 bit/s | 8.68 μs | Yes | V.34 modem with V.42bis compression low cost serial V.90/V.92 modem with V.42bis or V.44 compression |
128,000 bit/s | 7.81 μs | Yes | |
230,400 bit/s | 4.34 μs | No | LocalTalk high end serial V.90/V.92 modem with V.42bis or V.44 compression[23][24] |
256,000 bit/s | 3.91 μs | Yes | |
460,800 bit/s | 2.17 μs | No | [citation needed] |
Wikibooks has a book on the topic of: Programming:Serial Data Communications |