Download TNT4882 Programmer Reference Manual

Appendix C
Introduction to the GPIB
Determining the PPE Message
The PPE message contains the parallel poll configuration data for a device. Table C-2
shows how you determine the value of DIO[7:1] for the PPE message. As with all
commands, the DIO[8] is a don't care bit.
Table C-2. Determining the PPE Message
Sense Bit (S)
PPR Message
to Send
PPE Message
(hex)
0
0
0
0
PPR1
PPR2
PPR3
PPR4
60
61
62
63
0
0
0
0
PPR5
PPR6
PPR7
PPR8
64
65
66
67
1
1
1
1
PPR1
PPR2
PPR3
PPR4
68
69
6A
6B
1
1
1
1
PPR5
PPR6
PPR7
PPR8
6C
6D
6E
6F
Physical Representation of the PPR Message
To send a PPR message true, a device drives the corresponding GPIB DIO signal low
with an open-collector driver. For example, to send the PPR4 message true, a device
drives the GPIB DIO4 signal low.
Because devices drive the DIO signals with open-collector drivers during parallel polls,
more than one device can share a PPR message. If a Controller detects a PPR message
being sent true, the Controller knows that one or more of the devices sharing the PPR
message is sending the PPR message true.
© National Instruments Corp.
C-27
TNT4882 Programmer Reference