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DTM-3200 – OEM Ethernet TSoIP Converter
User Manual
Figure 6 below shows the structure of a command written through the serial interface. If
command is a read-command, the data may be omitted. If the category does not require an index
the index must be omitted.
All commands successfully sent to the DTM-3200 are answered with a copy of the comm
including the data bytes.
When an incorrect checksum is detected, the DTM-3200 will not return an answer. When protocol
errors are detected, e.g. a combination of a valid category with an invalid setting, the R/W byte of
the reply is replaced with the ASCII character 'E' and the data is removed from the message.
4.2.2 Command protocol on I
Field
Format
Start
S
Address
I
2
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
6
The DTM-3200 supports a single channel only. Whenever index is used as a channel number, it shall/will be set to 0.
Figure 6. Command on an RS-XXX serial control interface
2
C
Standard I
2
C start condition
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
(Optional) 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
2
C stop condition. A repeated start condition can
be used at all times to concatenate multiple I
actions
20
Description
2
C R/W bit, which is set to
6
2
C read / write
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