CityGrow CG102RS232, Руководство пользователя

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5. Serial Data Format
The data format of serial interface is shown in Figure 3-1.
Sync Length
Frame
Control
Seq.
No.
Payload Check Sum
2 bytes 2 bytes 1 byte 1 byte 1 byte 0 - 20 bytes
Paddin
g
1 byte
Figure 5-1 Data format of the serial interface
The data frame of the serial interface comprises of different fields, which are summarized
in the following table (Table 3-1):
Table 5-1 Summary of fields in the data frame
Field Description Size
Sync Sync-code 2 bytes
Length Length of data frame 1 byte
Frame Control Used for the frame acknowledgement 1 byte
Seq. No. Sequence number of the data frame 1 byte
Padding Padding field contain of ‘0’ 1 byte
Payload Payload reserved for Protocol Data Unit of ZDCP 1 – 20 bytes
Check Sum Check sum code for error detection 2 bytes
5.1. Sync
The 2-byte sync-code is used to indicate the start of the data frame. The format of the
sync-code is shown in Figure 3-2.
0x19 0xC3
1 byte 1 byte
Sync
Figure 5-2 Format of the sync-code
5.2. Length
The 1-byte data frame length is used to indicate the total length of the data frame in term
of number of byte. The length is counted start from the “Frame Control” to the end of the
“Payload”.
5.3. Frame Control
The 1-byte frame control is used to indicate whether the data frame is required to be
acknowledged by the receiver after the receiver received the data frame correctly. The
format of the frame control is shown in Figure 3-3.
Ack
Req
Reserved
6 bit 1 bit
Frame Control
Is
Ack
1 bit
Figure 5-3 Data format of the frame control