Specifications

3. R-COMMENT [variable length, ASCII]. The definition of this field depends on R-RESPONSE
and the message TYPE. If R-RESPONSE is “R”, then this field shall be used to send error
codes or log messages, as specified by the subsystem ICD or other subsystem design documents.
6 Command/Response Examples
For clarity in the following examples, single quotes (’) are used in lieu of s paces and “@” is used to
represent a byte of raw binary data.
6.1 PNG Command/Response
The following is an example of a PNG command sent from MCS to DP. MCS sends a message packet
containing the payload
DP’MCSPNG’’’’’1391’’’0’54828’12345678’
which is interpreted as follows:
• DESTINATION is the DP subsystem.
• SENDER is MCS.
• TYPE = “PNG”
• REFERENCE = 1391
• DATALEN = 0, so the DATA field is empty.
• MJD = 54828, so Dec 28, 2008 UT.
• MPM = 12345678. Dividing by 3600 × 1000 gives the number of hours past UT midnight; in
this case, about 3.4.
• Mandatory space following the MPM field.
• The DATA field is empty.
In response, DP sends the message
MCSDP’PNG’’’’’1391’’’8’54828’12345698’A’NORMAL
which is interpreted as follows:
• DESTINATION is the MCS subsystem.
• SENDER is DP.
• TYPE = “PNG”
• REFERENCE = 1391 (same as the command message, so MCS can identify it)
• DATALEN = 8, so the DATA field is 8 bytes long.
• MJD = 54828 (same as the command message since the response occurs the same UT day)
• MPM = 12345698; this is DP’s estimate of when this response was sent.
• Mandatory space following the MPM field.
• The DATA field contains the 8-byte string “A’NORMAL”, indicating that the associated com-
mand message was accepted, and that the value of MIB entry 1.1 (SUMMARY) is “NORMAL”.
6