HP 16500C Programmer's Manual page 120

Common Commands
*ESR (Event Status Register)
Table 9-3 shows the Standard Event Status Register. The table details the
meaning of each bit position in the Standard Event Status Register and the
bit weight. When you read Standard Event Status Register, the value
returned is the total bit weight of all the bits that are high at the time you
read the byte.
Table 9-3 Standard Event Status Register
Bit Position
7
6
5
4
3
2
1
0
9–8
Bit Weight Bit Name Condition
128 PON 0 = register read - not in power up mode
1 = power up
64 URQ 0 = user request - not used - always zero
32 CME 0 = no command errors
1 = a command error has been detected
16 EXE 0 = no execution errors
1 = an execution error has been detected
8 DDE 0 = no device dependent errors
1 = a device dependent error has been detected
4 QYE 0 = no query errors
1 = a query error has been detected
2 RQC 0 = request control - not used - always zero
1 OPC 0 = operation is not complete
1 = operation is complete