Gamma Vacuum DIGITEL, Instruction Manual

Page: 27 / 43

Field Size Comment
6 TERMINATOR 1 ASCII hex character ASCII carriage return
ASCII value of carriage return character placed at the end of a command packet.
There is not a space between the checksum and terminator field.
Note:
Checksum field can be bypassed by specifying “00”.
9.2. Gamma protocol response packet structure over serial connection
The response packet is made up of at least five fields and contains
information to let the controlling computer know the command requested
was either recognized and accepted (STATUS = “OK”), or an error condition
occurred (STATUS = “ER”). The minimum packet also contains a RESPONSE
CODE that is used either to pass an error code (if STATUS = “ER”), or is
available for each unit to use as needed for a STATUS return of “OK”. The
minimum response packet (simple acknowledgment with no data) would
consist of the following fields, and would be 12 bytes long.
Table 4. Response packet structure over serial connection
Address space Status space Response
code
space Response
data
space Checksum Terminator
2 bytes 1 byte 2 bytes 1 byte 2 bytes 1 byte variable 1 byte 2 bytes 1 byte
Field Size Comment
1 ADDRESS 2 ASCII hex characters Range 00 through FF
This field is filled in with the hexadecimal representation of the integer address of
the unit. The range provides 255 unique addresses. The controlling computer will
use this field to determine that the correct remote unit is responding.
2 STATUS 2 ASCII hex characters Either OK or ER
This field is made up of two ASCII characters and is either OK or ER. OK indicates
success in recognizing the command. ER indicates an error condition followed by an
error code (See Table: Response codes ).
3 RESPONSE CODE 2 ASCII hex characters Range 00 through FF
See Table: Response codes for description of possible response codes.
4 RESPONSE DATA As needed ASCII printable characters
only
Data field(s) are used to respond to commands requesting data. Data must be in
ASCII printable format. There is no limit on the number or size of data fields. Data is
not required for all responses.
5 CHECKSUM 2 ASCII hex characters Computed checksum of
packet
Checksum contains a simple computed checksum of the response packet. See CRC
checksum example on page 28 for details.
6 TERMINATOR 1 ASCII hex characters ASCII carriage return
ASCII value of carriage return character placed at the end of a packet. There is not a
space between the checksum and terminator field.
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900035_B - Serial communication