Parallel Poll Register (Ppr) - National Instruments Corporation GPIB-1014P User Manual

Section Four

Parallel Poll Register (PPR)

VMEbus Address:
AUXMR Control Code: 011 (Binary, Bits 7 - 5)
Attributes:
4 3
U S
Writing to the Parallel Poll Register is done via the AUXMR. Writing the binary value 011 into the
Control Code (CNT[2-0]) and a bit pattern into the command code portion (COM[4-0]) of the
AUXMR causes the command code to be written to the Parallel Poll Register (PPR). When
COM[4-0] is written to the PPR, the bits are named as shown above. This 5-bit command code
determines the manner in which the TLC responds to a Parallel Poll.
When using the remote Parallel Poll Configure (IEEE-488 capability code PP1), do not write to the
PPR. The TLC implements remote configuration fully and automatically without software
assistance. The hardware recognizes, interprets, and responds to Parallel Poll Configure (PPC),
Parallel Poll Enable (PPE), Parallel Poll Disable (PPD), and Identify (IDY) messages. The user
need only set or clear the individual status (ist) message (using Set/Clear Parallel Poll Flag auxiliary
commands) according to pre-established system protocol convention. Writing to the PPR after it is
remotely configured will corrupt the configuration.
When using the local PPC (capability code PP2), a valid PPE or PPD message should be written to
the PPR in advance of the poll.
Bit Mnemonic
4w U
© National Instruments Corporation
Base Address + B (hex)
Write Only,
Accessed through AUXMR
2 1
P3 P2
Description
Parallel Poll Unconfigure Bit
The U bit determines whether or not the TLC participates in a Parallel
Poll. If U=0, the TLC participates in Parallel Polls and responds in the
manner defined by PPR[3] through PPR[0] and by ist. If U=1, the TLC
does not participate in a Parallel Poll.
The U bit is equivalent to the local message lpe* (local poll enable, active
low). When U=0, S and P3-1 mean the same as the bit of the same
name in the PPE message, and the I/O write operation (to the PPR) is the
same as the receipt of the PPE message from the GPIB Controller.
When U=1, S and P3-1 do not carry any meaning, but they must be
cleared.
4-37
0
P1
W
Register Descriptions
GPIB-1014P User Manual