Terumo CDI 550 Operator's Manual page 139

C-8 appendix c
Serial Packet Interface Structure.
The format of a packet will be:
where:
<STX> - Start of packet character, which will be character 0x02 (binary, not
ASCII '2').
A - Single Character defining the device ID. See Device ID section for
details.
BB - 8-bit ASCII hex-encoded sequence value.
LLLL - 16-bit ASCII hex-encoded length value. Length is calculated as the
length of the entire packet from the <STX> to the <ETX> inclusive.
C - Single ASCII character Command. This will define the major cat-
egory for the packet. See the Command list section for definitions.
S - Single ASCII number SubCommand. This will define the specific
request or action under the category of the previously defined
Command character. See the SubCommand list section for defini-
tions.
D...D - Variable-length data field in ASCII format. The data field will be
used to pass parameters if necessary. If no data is necessary, this
field will be omitted.
ZZ - 8-bit ASCII hex-encoded CRC. This CRC is calculated using the
entire packet up to, but not including, the CRC field. Refer to the
CRC calculation section for how to calculate the CRC.
<ETX> - End of packet character, which will be character 0x03 (binary, not
ASCII '3').
Device IDs.
Device IDs are single ASCII characters denoting specific device types for communica-
tion. Since communication on the Serial Port using the Packet protocol could be with
any type of device capable of receiving analyte information, the Device IDs for incom-
ing Packets are ignored, and are only kept in the packet for compatibility with the CDI
Pump Interface Protocol (see pump interface section).
The Device ID chosen for the System 550 is 'X' . All outgoing packets from the CDI
System 550 will have an 'X' in the Device ID field.
<STX>ABBLLLLCSD...DZZ<ETX>