National Instruments Printer Accessories 320030-01 用户手册
Chapter 6
Theory of Operation
© National Instruments Corporation
6-3
GPIB-1014 User Manual
Control Equations of Transceivers
Table 6-1 lists the control equations for the address and data.
Table 6-1. Control Equations of Transceivers
VMEbus Signals
Transceivers
Control Equations
A23 through A16
AS573
OC* = OWN* (output enable)
C = UAS (input clock)
C = UAS (input clock)
A15 through A8
AS573
OC* = OWN* (output enable)
C = UAS (input clock)
C = UAS (input clock)
A7 through A1
F245
EN* = low (output enable)
DIR = OWN (transceiver's direction)
DIR = OWN (transceiver's direction)
HIBYTE transceiver
F245
EN* = HIBYTE*
DIR = (BWR* & OWN*) + (BWR &
DIR = (BWR* & OWN*) + (BWR &
OWN)
AM lines, IACK*, LWORD*
F241
EN* = OWN*
D15 through A8
F245
EN* = (ACKEN* & DBEN*) +
NEW_CYCLE* + DIACK
DIR = (BWR* & OWN*) + (BWR &
NEW_CYCLE* + DIACK
DIR = (BWR* & OWN*) + (BWR &
OWN)
D7 through D0
F245
EN* = (((ACKEN* & DBEN*) +
NEW_CYCLE*) & (BRDEN* + DS*)) +
HIBYTE
DIR = (BWR* & OWN*) + (BWR &
NEW_CYCLE*) & (BRDEN* + DS*)) +
HIBYTE
DIR = (BWR* & OWN*) + (BWR &
OWN)
Address Decoding
During non-DMA operations, the GPIB-1014 acts as a VMEbus slave and monitors the lower 16
lines of the VMEbus address bus (A15 through A01), the Address Modifier Lines (AM5 through
AM0), and the VMEbus signals LWORD* and IACK*. Receivers and comparators are used to
recognize the GPIB-1014 base address during short I/O transfers.
lines of the VMEbus address bus (A15 through A01), the Address Modifier Lines (AM5 through
AM0), and the VMEbus signals LWORD* and IACK*. Receivers and comparators are used to
recognize the GPIB-1014 base address during short I/O transfers.
Two 25LS2521 comparators recognize the short I/O base address of the GPIB-1014. Except for
Model 1S, the base address is selectable with jumpers located on the board or with strapped lines
routed to the P2 connector. The base address of the GPIB-1014 is recognized whenever the
VMEbus signal AS* is active (IACK* is inactive), the Address Modifier lines indicate a short
I/O operation, and VMEbus address lines A15 through A9 match the jumper selected base
Model 1S, the base address is selectable with jumpers located on the board or with strapped lines
routed to the P2 connector. The base address of the GPIB-1014 is recognized whenever the
VMEbus signal AS* is active (IACK* is inactive), the Address Modifier lines indicate a short
I/O operation, and VMEbus address lines A15 through A9 match the jumper selected base