Allen-Bradley 825-PR12D Manual page 11

Data Packet Definition
The 825-PR12D sends a binary data packet approximately every 0.6 seconds (0.75
seconds maximum). The packet contains data for all four types of supported RTDs, so
no settings are required in the 825-PR12D. The data packet is transmitted over a
fiber-optic cable to the 825-P.
Table 3 825-PR12D RTD Scanner Data Packet Definition
Data Value Data Size
A546h 2 bytes
74h 1 byte
0000000000h 5 bytes
00h 1 byte
12h 1 byte
00h 1 byte
00h 1 byte
xxxxxxx 4 bytes
xx 2 bytes
xxxx 96 bytes
yy 2 bytes
a
2 bytes per word • 4 words per RTD • 12 RTDs = 96 bytes.
Date Code 20080722
Description
Beginning of Message Code
Message Length (116 bytes)
Routing Value (0)
Status Byte
Function Code
Sequence Byte
Pad Byte
Milliseconds Since 825-PR12D Power-Up or Clock
Rollover (86,400,000 ms/5265C00h)
Device Status (Bitmap)
Bit 0: Power Supply Status
Bit 1: RTD Circuitry Status (0 = okay; 1 = fail)
Bit 2: Watchdog Timer Status (0 = okay; 1 = fail)
Bit 3: 8 V Power Supply Status (0 = okay; 1 = fail)
Bit 4: 5 V Power Supply Status (0 = okay; 1 = fail)
Bit 5: –5 V Power Supply Status (0 = okay; 1 = fail)
Bits 6–15: Unused, Zero
a
Temperature Data (°C)
Word One: PT100 temperature
Word Two: NI100 temperature
Word Three: NI120 temperature
Word Four: CU10 temperature
Four words are sent for each of the 12 inputs. Use only
the appropriate temperature for the type of RTD con-
nected to each input.
If an RTD circuit is open, the error code 7FFFh is sent;
if the circuit is shorted, the error code 8000h is sent.
For the first four seconds after power is applied to the
scanner, it sends the error code 7FF0h.
CRC-16 Data Block Check Code
Data Packet Definition
825-PR12D RTD Scanner
11