Measurement Computing Digital488 - Manual (Page 54)

Section 3 Command Descriptions
3.24
Serial Poll Status Byte
The Serial Poll Output byte is sent upon receiving the serial poll command
from the controller. Refer to the SRQ description for details on how the Serial Poll
byte is affected. Below is a description of the significance of each bit in the Serial Poll
byte.
Bit Location Significance (SRQ Bit Value if set to logic 1)
DIO1(LSB)
1 Service Input transition
DIO2 2 EDR input transition
DIO3 4 Bus error
DIO4 8 Test error
DIO5 16 Ready for more commands
DIO6 32 not assigned, always 0
DIO7 64 Service Request bit
DIO8 (MSB) 128 not assigned, always 0
Serial Poll Bit Description
DIO1 When enabled by the M1 command, DIO1 is set by a transition on the Service
Input line (active transition state determined by the Invert command (I64)).
DIO1 is cleared after the controller serial polls the Digital488.
DIO2 When enabled by the M2 command, DIO2 is set on an EDR transition (active
transition state determined by the Invert command (I32)). DIO2 is cleared
after the controller serial polls the Digital488.
DIO3 DIO3 is set when an invalid command is sent to the Digital488. The M4
command will enable a Service Request to occur then an invalid command is
received. The bit is cleared after the controller sends a Status command (U0X)
and reads the status string from the Digital488.
DIO4 The status of DIO4 is determined after the Test command (T0X) is sent to the
Digital488. If the self test passes, the DIO4 bit will remain a zero. If the self
test fails, DIO4 will be set to a logic 1.