Chapter 4
Theory of Operation
©
National Instruments Corporation
4-3
PCI-DIO-96/PXI-6508/PCI-6503 User Manual
PCI Interface Circuitry
Your DIO board uses the PCI MITE ASIC to communicate with the
PCI bus. The PCI MITE ASIC was designed by National Instruments
specifically for data acquisition. The PCI MITE is fully compliant with
PCI Local Bus Specification
, Revision 2.1.
The base memory address and interrupt level for the board are stored inside
the PCI MITE at power on. You do not need to set any switches or jumpers.
82C55A Programmable Peripheral Interface
The 82C55A PPI chip is the heart of your DIO board. The PCI-DIO-96 and
PXI-6508 contain four PPIs. The PCI-6503 contains one PPI. Each of these
chips has 24 programmable I/O pins that represent three 8-bit ports: PA,
PB, and PC. Each port can be programmed as an input or output port. The
82C55A has three modes of operation: simple I/O (mode 0), strobed I/O
(mode 1), and bidirectional I/O (mode 2). In modes 1 and 2, the three ports
are divided into two groups: group A and group B. Each group has eight
data bits, plus control and status bits from port C (PC). Modes 1 and 2 use
handshaking signals from the computer to synchronize data transfers. Refer
to Appendix B,
, for more detailed
information.
Different revisions of the PCI-DIO-96, PXI-6508, and PCI-6503 use
different 82C55A chips from Intersil Corporation or OKI Semiconductor.
For the most recent data sheet for the Intersil CMS82C55A or CS82C55A,
visit
www.intersil.com
. For the most recent data sheet for the OKI
MSM82C55A, visit
www2.okisemi.com
.
Table 4-1 describes the 82C55A used in the PCI-DIO-96, PXI-6508, and
PCI-6503.
Table 4-1.
The 82C55A Chips Used in the PCI-DIO-96, PXI-6508, and PCI-6503
Type
Bus Hold
†
PCI-DIO-96
PXI-6508
PCI-6503
Intersil
CMS82C55A
No
Revision K or later
Revision G or later
Revision G or later
Intersil
CS82C55A
Yes
182920H-01
184836E-01
185183E-01
OKI
MSM82C55A
No
182920J-01,
revision G or earlier
184836F-01,
revision D or earlier
185183F-01,
revision D or earlier
†
Indicates whether the chip has the bus hold feature on the port pins.