Company Confidential
23
Raveon Technologies Corp.
1
Start of Header (SOH)
1 (0x01)
Indicates beginning of a frame
1
1
Control Field
*1
0x42
Indicates a Receive Data WMX message
2
0-6
Destination Address
ID in ASCII
hex, 0000-
FFFFFF
6 ASCII HEX representation of the decoded CAP code. For
example, cap code 279001 will be represented in the field as
441D9.
1
Separator 1 (
!
)
33 (0x21)
Field separator character 1.
3
0-4
Source Address
(Optional when
transmitting)
Null (no byte)
This field is unused in POCSAG Decode
1
Separator 3 (
#
)
35 (0x23)
Field separator character 3
(when transmitting, may be left out if sequence field is not used)
5
0-4
Sequence
ASCII number
0-255
A sequence number for this reception to uniquely identify it.
Increments every reception.
1
Separator 4 (
$
)
36 (0x24)
Field separator character 4
6
0-16
RSSI Field
ASCII digits
RSSI Information about this reception. Units in negative dBm.
1
Start of Text (SOT)
2 (0x02)
Indicates beginning of data
7
1-500
Data Field
The data bytes sent/received by the user. May be any binary data
bytes except the DLE ETX sequence.
See Binary Encoding
section on how to send 8-bit binary data.
2
End of Text
( DLE ETX )
16 (0x10)
3 (0x03)
ETX end of the data frame
8
0 - 4
ASCII hex Checksum
(Optional)
Variable
0-FFFF
The 16-bit checksum of all the previous bytes, starting with the
SOH through the end of the data bytes, not including DLE/ETX.
Most significant digit first.
1
End of Transmission
(EOT)
4 (0x04)
Indicates end of the frame
8. Using the M8T – Packet Data Mode
This section describes the operation of the M8T when it is in the
Packet Mode
of
operation. It is the easiest and most reliable mode of operation for a data
modem.
In Packet Mode, all transmissions are sent in bursts or packets, and contain
address, error detection, and error correction information. Date enters the M8T
modem’s serial I/O port, and is stored in a buffer within the modem until it is
ready to be transmitted. Packetized operation has these advantages over non-
packet modems:
Packet Mode Advantages
1.
Error Detection
The modem uses a 16-bit CRC at the end of every packet
of data. The CRC is used to check the data for errors, and if there are any
errors, the data will not be passed onto the user.
2.
Error Correction
Automatic error correction may be used.
M8T
modems
incorporate an optional ARQ method to re-transmit packets with error, to
ensure the user’s data is delivered error-free.
