CMOSTEK CMT2250A, Configuration Manuallines

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
Address (Sync ID)
The Sync ID is sent and received starting from the LSB. For example, if the “Sync ID Length” is set to 16 and the “Sync ID Value”
is set to 1, the binary value of the Sync ID is “0000 0000 0000 0001”. In this case, bit<0> = 1 is received first and bit<15> = 0 is
received at the end of the Sync ID field.
 D0, D1, D2, D3
These are the 4 data bits D0, D1, D2, D3 received to control the data pins. D0 is received first.

CRC
The 8-symbol CRC field can increase the reliability of the communication, while it also increases the entire packet length. The
CRC is calculated on the address (Sync ID) field and the data (D0 – D7) field of the Normal Packet, and is only calculated on the
address (Sync ID) field of the Study Packet (See below section). The CRC polynomial is:
CRC Polynomial = X8 + X5 + X4 + 1
x
7
x
6
x
5
x
4
x
3 3
x
2
x
1
x
0
Data input
Figure 27. 1920 CRC Algorithm Structure
5.1.2 1920 Study Packet Structure
The study packet is used for the device to learn the Sync ID from the transmitter in order to pair with the transmitter. It contains an
optional Preamble, a 32-symbol Head_S, a Sync ID and an optional 8-symbol CRC.
Preamble
16-symbol
CRC
8-symbol
Head_S
32-symbol
Address (Sync ID)
configurable 1-32 bits
Figure 28. 1920 Study Packet Structure
The Study Packet structure is not illustrated on the RFPDK since the settings of Preamble, Sync ID and CRC are identical to
those of the Normal Packet. Differing from the Head_N in the Normal Packet, the Head_S indicates the current packet is a Study
Packet. Also, the Study Packet does not contain the data field. The pattern of Head_S is shown below:
2
SYM
2
SYM
2
SYM
2
SYM
2
SYM
2
SYM
1
SYM
1
SYM
1
SYM
1
SYM
2
SYM
1
SYM
1
SYM
2
SYM
2
SYM
2
SYM
2
SYM
2
SYM
2
SYM
Figure 29. 1920 Head_S Pattern
5.1.3 1920 Bit Format
In 1920 packet, a single bit can be constructed (encoded) by 3, 4, 5 or 6 symbols. The user can select the desired value of the
“Bit Format” parameter on the RFPDK. Please note that only the Sync ID field and the D0, D1, D2, D3 field have the unit of “bit”.