| PC 9-way D-type |
RS232 levels |
TTL levels |
|||||||||||
| +12V | --> | VDD | 1 | U SN75 --185-- |
20 | VCC | --> | +5V | |||||
| o | 1 | --> | DCD | --> | RA1 | 2 | 19 | RY1 | --> | !DCD | |||
| 6 | o | --> | DSR | --> | RA2 | 3 | 18 | RY2 | <-- | !DSR | |||
| o | 2 | --> | RX | --> | RA3 | 4 | 17 | RY3 | --> | SI | |||
| 7 | o | <-- | RTS | <-- | DY1 | 5 | 16 | DA1 | --> | !RTS | |||
| o | 3 | <-- | TX | <-- | DY2 | 6 | 15 | DA2 | <-- | SO | |||
| 8 | o | --> | CTS | --> | RA4 | 7 | 14 | RY4 | <-- | !CTS | |||
| o | 4 | <-- | DTR | <-- | DY3 | 8 | 13 | DA3 | --> | !DTR | |||
| 9 | o | --> | RI | --> | RA5 | 9 | 12 | RY5 | <-- | !RI | |||
| o | 5 | 0V | -12V | --- | VSS | 10 | 11 | GND | --- | 0V | |||
This suits the PC which needs 3 transmitters and 5 receivers!
Note the CMOS version consumes much less current (160uA instead of 30mA) but costs much more.