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5 - 4
SE4750 Integration Guide
Command Checksum
Every command must include a checksum, calculated as follows:
Sum the bytes in the command, starting from the opcode through the last command data byte.
1.
Use only the low byte of this result.
2.
Perform a 2's complement of this result.
3.
This value is the checksum and is added to the checksum field of the command.
Response Status Code
Every response includes a status code that indicates the success of the command. A successful command returns
an ACK or 0x80.
Table 5-2
lists status codes for single errors. Note that these error codes are bit positions within the status byte,
and two errors can occur (e.g., NAK and AIM_POWER_FAIL), resulting in values not listed in this table.
Response Status Codes
Table 5-2
Status
ACK
NAK
CKSM_ERR
AIM_POWER_FAILURE
THERMAL_FAILURE
INTERNAL_I2C_FAILURE
Value
0x80
Command was successful.
0x82 (Bit 1 set)
Command failed. Possible causes are:
•
•
•
0x84 (Bit 2 set)
The transmitted checksum did not match the checksum of the
data.
0x88 (Bit 3 set)
The aiming power exceeded its limit.
0x90 (Bit 4 set)
The internal temperature exceeded its limit.
0xA0 (Bit 5 set)
The internal I
Cause / Meaning
Invalid opcode
Invalid command format
Invalid parameter value
2
C interface failed.
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