Measurement Computing Digital488 - Manual (Page 55)

Section 3 Command Descriptions
3.25
The M8 command will cause a Service Request to be generated in addition
to DIO4 being set if the self test fails. The DIO4 bit is cleared after the
controller sends a Status command (U0X) and reads the status string from
the Digital488.
DIO5 The DIO5 bit is set after an entire command string has been received and
processed by the Digital488. The bit is clear while the Digital488 is
processing commands which have been received from the controller. When
used with the M16 command, a Service Request will also be generated
when the DIO5 bit is set. An Execute command (X) must be received
before the DIO5 bit can be cleared.
DIO6 DIO6 is not used, and is always a logic zero.
DIO7 When the Digital488 generates a Service Request, the DIO7 will be set to a
logic one. This is used by the controller to determine that the Service
Request was generated by the Digital488.
DIO8 DIO8 is not used, and is always a logic zero.
Example:
CLEAR 718 reset the Digital488
OUTPUT 718;"M4X" select SRQ on Bus error
OUTPUT 718;"F7X" send an invalid bus command.
ERROR and SRQ LEDs should illuminate
SPOLL (718) display should be 84 (64+16+4)
64 denotes the Digital488 was the source of the SRQ. 16 denotes the Digital488 is
READY for more commands. 4 denotes a Bus error.
When serial polled,the SRQ LED will turn off.