PELCO "P" PROTOCOL
GENERAL
This section describes the protocol used when sending commands to an Intercept Dome in the “P” version protocol. The protocol uses no parity, one start bit, eight data bits, and one stop bit. The recommended baud rate is 4800 （4800, 8, N, 1, 1）.
MESSAGE FORMAT
| Byte | Value | Function |
| 1 | $A0 | STX （start transmission） |
| 2 | $00 to $1F | Address |
| 3 | Data byte 1 | （see below） |
| 4 | Data byte 2 | （see below） |
| 5 | Data byte 3 | （see below） |
| 6 | Data byte 4 | （see below） |
| 7 | $AF | ETX （end transmission） |
| 8 | $00-$FF | Check Sum |
Byte 1 is always $A0
Byte 2 is the receiver address, set by DIP switch in the receiver
Byte 3-6, see below
Byte 7 is always $AF
Byte 8 is an XOR sum of Bytes 2-6
The protocol is “zero indexed” so that the hexadecimal address sent in the protocol for the first receiver is $00 which corresponds to address 1.
The bits within the “Data bytes” are broken up into two main groups. For Pan and Tilt commands, the functions are determined as follows:
PAN AND TILT COMMANDS
| | Bit number |
| | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| Data 1 | 0 | Camera On | Autoscan On | Camera on / off | Iris Close | Iris Open | Focus Near | Focus Far |
| Data 2 | 0 | Zoom Wide | Zoom e | Tilt Down | Tilt Up | Pan Left | Pan Right | 0 （for pan / tilt） |
| Data 3 | Pan Speed $00 to $3F and $40 for Turbo |
| Data 4 | Tilt Speed $00 to $3F |
EXTENDED COMMAND SET
The extended command set will have bit 0 of data byte 2 set and will follow the format in the following table:
| Command | Data byte 1 | Data byte 2 | Data byte 3 | Data byte 4 |
| Set Preset XX | 00 | 03 | 00 | 01 to FF |
| Clear Preset XX | 00 | 05 | 00 | 01 to FF |
| Go To Preset XX | 00 | 07 | 00 | 01 to FF |
| Flip （rotate 180º） | 00 | 07 | 00 | 21 |
| Zero Pan Position | 00 | 07 | 00 | 22 |
| Set Aux XX | 00 | 09 | 00 | 01 to 08 |
| Clear Aux XX | 00 | 0B | 00 | 01 to 08 |
| Remote Reset | 00 | 0F | 00 | 00 |
| Zone Start | 00 | 11 | 00 | 01 to 08 |
| Zone End | 00 | 13 | 00 | 01 to 08 |
| Write char to screen | 00 | 15 | 0 to 28 | 0 to 7F |
| Clear Screen | 00 | 17 | 00 | 00 |
| Alarm Ack | 00 | 19 | 00 | 01 to 08 |
| Zone Scan On | 00 | 1B | 00 | 00 |
| Zone Scan Off | 00 | 1D | 00 | 00 |
| Pattern Start | 00 | 1F | 00 | 00 |
| Pattern Stop | 00 | 21 | 00 | 00 |
| Run Pattern | 00 | 23 | 00 | 00 |
| Zoom Lens Speed | 00 | 25 | 00 | 00 to 03 |
| Focus Lens Speed | 00 | 27 | 00 | 00 to 03 |
The receiver will respond with an ACK.
To accommodate features of new systems and maintain compatibility with our old systems, some functions have been added through the use of some of the unused preset functions. These are:
| Preset Number | Function |
| 99 | Begin Auto-scan |
| 98 | Begin Frame Scan |
| 97 | Begin Random Scan |
| 96 | Stop Scan |
| 95 | Enter Menu Mode |
| 94 | Remote Reset |
| 93 | Set Right Limit Stop |
| 92 | Set Left Limit Stop |
| 34 | Home （return to 0 pan position） |
| 33 | Flip |
Examples:
To SET PRESET 32 in the receiver with address 1, the command string （in Hexidecimal） would be:
A0 01 00 03 00 20 AF 17 （the last byte is the XOR sum of bytes 2 through 6）
To drive receiver with address 2 LEFT at half speed:
A0 02 00 04 00 1F AF 19
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