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DTM-3237B – DVB-S2X Receiver with DVB-ASI Output
User Manual
4.2.2 Message Format on I
Field
Start
S
2
Address
I
C address byte 7-bit I
Category
1 byte
Setting
1 byte
Read/Write
1 byte
Index
2 bytes
Data
n bytes
Checksum
1 byte
End
P
Figure 3 below shows the sequence to send a command over I
below, grey areas in the timing diagrams are sent by the DTM-3237B, while white areas are sent by
2
the I
C master. If the command is a read-command, the data may be omitted. Note that some settings
require an index.
Figure 3. Command (upper sequence) and response (lower) sequence for I
The DTM-3237B supports a single channel only, so when index is used as a channel number, it's always 0.
6
2
C
Format
Standard I
2
C address followed by the I
0 and 1 in the command- and response sequence
respectively
Selects a "category" of settings
Selects a setting within the selected category
0x01 for read and 0x00 for write
Provides an extra index parameter, e.g. to indicate the
channel number
The data written or read. The data length is variable for
each setting. In case of a write operation, the actual data is
returned as a (negative) acknowledgement
This is the least significant byte of the two's complement of
the sum of the 7-bit I2C slave address and all data-bytes in
the I2C message (excluding the checksum). The I2C R/W bit
is not included, an incorrect value of this bit would cause the
checksum to be not received at all.
Standard I
be used at all times to concatenate multiple I
actions
Description
2
C start condition
6
2
C stop condition. A repeated start condition can
2
C to the DTM-3237B. In the examples
17
2
C R/W bit, which is set to
2
C read / write
2
C
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