84
4-10 PARAM_REQUEST
Description: Request values of selected parameters
Packet Format
Length
Opcode
Status
Option code
Checksum
0x3F
(‘?’)
Field Descriptions
Table 4-12 Field Descriptions
Field
Name
Format
Size
Description
Length
Length of message (not including
checksum).
1 Byte
Length Field
Opcode
0x3F
1 Byte
Identifies this opcode type.
Status
Bit 0
：
Retransmit
Bit 1-5
：
Query property of the
parameter
Bit 6
：
Unused
Bit 7: Command source
1 Byte
Bit 0: Identifies the transmission status.
Bit1-5
：
Control querying the property of
parameter
0, Query maximum value of the
parameter
1, Query minimum value of the
parameter
2, Query permanent setting value of the
parameter
3, Query temporary setting value of the
parameter
4, Query the default value of the
parameter
5-15,Reserved.
Bit 6: Reserved to be 0.
Bit 7: 1, Command is from the host.
Option
code
ASCII value of the option code
Variable
Each option code has 4 bytes, the
scanner can query several parameters.
Parameter 1, Parameter 2…
Checksum
2's complement sum of message
contents excluding checksum.
2 Bytes Checksum of message.
The host uses this message to request selected parameters from the scanner.
Host Requirements
The host requests the scanner’s current values for specific parameters by listing the parameter codes in
the Request Data field. If the host asks for a parameter value which is not supported by the scanner, the
scanner responses NAK.
The scanner’s response to this command is PARAM_SEND, not ACK. Depending on the time-out setting,
and the number of parameters requested, this reply may fall outside the programmable Host Serial
Response Time-out. If this occurs, this is not a time-out error. To compensate, increase the time-out.
Scanner Requirements
When the scanner receives this message, it processes the information by formatting a PARAM_SEND
message containing all requested parameters supported and their values. The programmable Host
Serial Response Time-out can be exceeded when processing this message, depending on the time-out
set and the number of parameters requested.
For example: the value of scanner parameter “0301” is 1, when host query information of the parameter
“0301”, the PARAM-REQUEST sent by host is as following:
Length
Opcode
Status
Parameter code
Checksum
0x07
0x3F
(‘?’)
0x80
0x30 0x33 0x30 0x31
(‘0’ ‘3’ ‘0’ ‘1’)
0xFE 0x76
the PARAM-SEND responded by scanner is as following:
