Chapter 2 General Description
© National Instruments Corporation 2-7 GPIB-1014 User Manual
Data Transfer Bus (DTB) Requester
The GPIB-1014 arbitrates for the DTB before each DMA transfer. The board is designed for you
to select, through software, one of four VMEbus request lines (BR0* through BR3*) using two
bits in Configuration Register 1. To maximize the capabilities of the DTB, the board can be
programmed to become a Release On Request (ROR) DTB master. Unless programmed, the
GPIB-1014 is a Release When Done (RWD) master.
VMEbus Modules Not Provided
Because the GPIB-1014 is not designed to be VMEbus System Controller, it does not have the
following modules:
• Bus Timer
• Arbiter
• Interrupt Handler
• IACK Daisy-Chain Driver
• System Clock Driver
• Serial Clock Driver
• Power Monitor
Diagnostic Aids
The GPIB-1014 is designed to allow stand-alone verification of I/O and DMA functions. See
Chapter 7, Diagnostic and Troubleshooting Test Procedures, for details.
Data Transfer FeaturesThe GPIB-1014 can be used to transfer data to and from the GPIB using Direct Memory Access
(DMA) and programmed I/O. The overall throughput is dependent upon the following
parameters:
• The number of GPIB commands sent
• The amount of time spent setting up the GPIB-1014 DMA transfers
• The size of the DMA data buffers (number of bytes transferred in one DMA operation)
• Operating system overhead
• Interrupt service time
• VMEbus memory response time (DS* low to DTACK* low)