DekTec DTM-3237 DVB-S2 Receiver - Manual (Page 16)

DTM-3237 – OEM DVB-S2 Receiver with DVB-ASI Output
User Manual
16
4.2.2 Command protocol on I 2 C
Field Format Description
Start S Standard I 2 C start condition
Address I 2 C address byte 7-bit I 2 C address followed by the I 2 C R/W bit, which is set to
0 and 1 in the command- and response sequence
respectively
Category 1 byte Selects a “category” of settings
Setting 1 byte Selects a setting within the selected category
Read/Write 1 byte 0x01 for read and 0x00 for write
Index 2 bytes Provides an extra index parameter, e.g. to indicate the
channel number 6
Data n bytes 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
Checksum 1 byte 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.
End P Standard I 2 C stop condition. A repeated start condition can
be used at all times to concatenate multiple I 2 C read / write
actions
Figure 3 below shows the sequence to send a command over I 2 C to the DTM-3237. In the examples
below, grey areas in the timing diagrams are sent by the DTM-3237, while white areas are sent by
the I 2 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 2 C
6 The DTM-3237 supports a single channel only, so when index is used as a channel number, it’s always 0.