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A sub-miniature DB-9 connector on the rear panel of the EIK CW Power Supply supports half-duplex RS-422 or RS-485 serial communication with an external computer.
| Pin Number | RS-422 | RS-485 |
| 1 | N.C. | N.C. |
| 2 | * | |
| 3 | R+ | R+/T+ |
| 4 | T+ | * |
| 5 | GND | GND |
| 6 | T- | * |
| 7 | RL** | RL** |
| 8 | * | |
| 9 | R- | R-/T- |
*For 2-wire RS-485 operation, jumper pins 2 and 4 (R+ to T+) and pins 6 and 8 (R- to T-)
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Command blocks are formatted as follows:
| STX | > | 0 | 1 | b | R | D | E | K | ETX | 0 | 1 | CR |
| Prefix | Address | blank | Command | Suffix | Checksum | Terminator | ||||||
All characters are 8-bit ASCII.
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Example message exchange:
HOST:
| STX | > | 0 | 1 | b | R | D | S | T | A | T | ETX | 0 | 1 | CR |
LOCAL:
| ACK | STX | > | 0 | 1 | b | S | T | A | T | U | S | = | 2 | 2 | ETX | CR |
- Command block begins with PREFIX and ends with TERMINATOR
- Command begins with SPACE and ends with SUFFIX
- Checksum is used to test for transmission errors
- ASCII character ">" is a delimiter
- STX=02d (02h)
- NAK=21d (15h)
- ETX=03d (03h)
- SPACE=32d (20h)
- ACK=06d (06h)