National Instruments Corporation GPIB-1014P User Manual page 77

Register Descriptions
Bit Mnemonic
1-0w HLDE
HLDA
GPIB-1014P User Manual
Description
Holdoff on END Bit
Holdoff on All Bit
HLDE and HLDA together determine the GPIB data receiving mode.
The four possible modes are as follows:
HLDE HLDA
0 0
0 1
1 0
1 1
In Normal Handshake mode, the local message rdy is generated when
data is received from the GPIB. When the received data is read from the
DIR, rdy is generated in Acceptor Not Ready State (ANRS), the RFD
message is transmitted, and the GPIB handshake continues.
In RFD Holdoff on All Data (HLDA) mode, RFD is not sent true after
data is received until the Finish Handshake (FH) auxiliary command is
issued. Unlike Normal Handshake mode, the RFD HLDA mode does
not generate the rdy message even if the received data is read through the
DIR; that is, the GPIB RFD message is not generated.
In RFD Holdoff on End mode, operation is the same as the RFD
HLDA, but only when the end of the data block (EOS or END message)
is detected; that is, the END message is received or, if REOS is set, the
EOS character received. Handshake holdoff is released by the FH
auxiliary command.
In continuous mode, the rdy message is generated when in ANRS until
the end of the data block is detected. A Holdoff is generated at the end of
a data block. The FH auxiliary command must be issued to release the
Holdoff. The continuous mode is useful for monitoring the data block
transfer without actually participating in the transfer (no data reception).
In continuous mode, the DI bit (ISR1[0]r) is not set by the reception of a
data byte.
4-40
Data Receiving Mode
Normal handshake
RFD holdoff on All Data
RFD holdoff on END
Continuous
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Section Four