Paradise Datacom HPAC-100-RM, Руководство по эксплуатации

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3-26 Operations Manual: HPAC-100/125/150/200/250-RM SSPA
3 Operation of Stand-Alone Unit
Report Unit Setups
Requests a complete listing of a particular unit’s setup information.
Type: QUERY
Pkt Length: 6
Destination: SSPA System Address
Source: M&C Address
Command: 0x36
Data:
Unit ID: (1 byte, integer)
[ 1 | 2 | 3 ]
Length: 8 bytes
Report Unit Software Revision Level
Requests the software revision level of a particular unit.
Type: QUERY
Packet Length: 6
Destination: SSPA System Address
Source: M&C Address
Command: 0x3C
Data:
Unit ID: (1 byte, integer)
[ 1 | 2 | 3 ]
Length: 8 bytes
Responses
When the M&C unit sends a query command, the SSPA responds with the re-
quested information. Some of the response packets contain data in 2’s complement
form or binary coded decimal (BCD) format. The following sections contain some
programming hints on how to interpret such data.
Interpreting 2’s complement data
The temperature data sent from the SSPA are 2’s complement integers. This per-
mits negative as well as positive temperatures to be transmitted. A discussion of 2’s
complement integers will not be given here, but a simple routine for interpreting such
data is given. The 2’s complement data byte can be decoded by sign extending the
packet byte to the length of the integer data type in the M&C’s machine. The following
example shows this technique for expanding the temperature data.
unsigned character buf; /* one byte of packet data */
int CTemp; /* temperature in Celsius */
buf = temperature byte from packet
if ( ( buf & 0x80 ) = = 0x80 )
/* if MSB is set */
CTemp = (int) (0xFF00 | buf); /* set all upper bits, 2-byte integer
else
CTemp = (int) buf;
/* temperature is a positive integer