IRIG Encoding External Data

IRIG Encoding
External Data
Tech Note 409
A Measurement Specialties 65210 Series Inertial Measurement System with built-in IRIG encoder can be used
to IRIG encode data received on its RS485 serial line. To configure a 65210 Series System channel to IRIG encode
external data, select the RCAL value as the channel’s input and set the channel filter to a high value (e.g. 10,000 Hz).
Once configured, commands sent to set the channel’s RCAL value will cause the value to be included in the IRIG
frames output by the 65210 Series System. 65210s allow up to16 bits of data to be encoded per sensor channel.
Six steps are required to set an RCAL value:
1. Send a Listen Command to enable the 65210 Series System to process commands
2. Wait for the 65210 Series System to acknowledge processing of the Listen Command
3. Send the address of the RCAL value to be changed to the 65210 Series System
4. Wait for the 65210 Series System to acknowledge processing of the new address
5. Send the new RCAL value to the 65210 Series System
6. Wait for the 65210 Series System to acknowledge setting of the new RCAL value
Multiple IRIG channels can be set in step 5 if they are contiguous. The example at the end of this Tech Note shows
channels 12 through 16 being set with a single command. Steps 3 thru 6 can be repeated to encode additional values
as long as they are not updated faster than the IRIG frame rate.
To ensure data integrity, each message sent to and received from a 65210 System is framed with an 8 bit command header
and a 16 bit CRC. The CRC16 is computed from the header and data and then appended to the message. ‘C’ code to compute
a CRC16 can be found in Tech Note 410. Invalid messages received by a 65210 System are discarded and not acknowledged .
• RCAL settings are typically located at addresses 0x0280 through 0x029f:
Chn
1
2
3
4
Address
0x0280
0x0282
0x0284
0x0286
Chn Address
5
0x0288
6
0x028A
7
0x028C
8
0x028E
Chn Address
9
0x0290
10
0x0292
11
0x0294
12
0x0296
Chn Address
13
0x0298
14
0x029A
15
0x029C
16
0x029E
• Each 16 bit value is stored and sent high byte first (e.g. channel 0 high byte is at 0x0280 and the low byte is
at 0x0281, 0x1234 is sent as 0x12, 0x34).
• Addresses are sent as 32 bit addresses, low byte first (e.g. address 0x00000290 is sent as 0x90, 0x02, 0x00,
0x00).
• CRCs are sent low byte first (e.g. 0x06C0 is sent as 0xC0, 0x06).
TN 409: IRIG Encoding External Data
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Example
IRIG Encoding Data Using 65210 Series System
Channels 12 through 16
Step
1
Sent by Controller
0x18
0x01
<crc>
<crc>
Listen
Device ID 1 (factory default ID)
CRC Low
CRC High
2
3
0x4C
0x96
0x02
0x00
0x00
<crc>
<crc>
0xAD
<data>
<data>
<data>
<data>
<data>
<data>
<data>
<data>
<data>
<data>
<crc>
<crc>
6
TN 409: IRIG Encoding External Data
precisionsensors.meas-spec.com 0x09
0xC0
0x06
Ack (listening)
CRC Low
CRC High
0x09
0xC0
0x06
Ack (new address set)
CRC Low
CRC High
0x09
0xC0
0x06
Ack (new values set)
CRC Low
CRC High
Send 4 byte RCAL address
Chn 12 address
CRC Low
CRC High
4
5
Reply from 65210 Series System
Write 10 bytes of data
Chn 12 High data byte
Chn 12 Low data byte
Chn 13 High data byte
Chn 13 Low data byte
Chn 14 High data byte
Chn 14 Low data byte
Chn 15 High data byte
Chn 15 Low data byte
Chn 16 High data byte
Chn 16 Low data byte
CRC Low
CRC High
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Akron OH 44333 PH : 330-659-3312 7/24/2013
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