Measurement Computing PCI-DIO24/S - Manual (Page 12)

12
Chapter 3
Functional Details
The PCI-DIO24/S board features the following:
 82C55 digital I/O chip interfaced to the PCI bus. The I/O pins of an 82C55 are bi-directional CMOS TTL
level.
 24-bits of digital I/O
 37-pin I/O connector
 Digital I/O and interrupt pins are protected from electrostatic discharges of up to ±15 kV (air) and
±8 kV (contact).
The 82C55 provides the 24-bit digital I/O channels into three eight-bit ports labeled Port A , Port B and Port C .
Port C is further divided into two four-bit ports. You can program each port for input or output.
PCI-DIO24/S functions are illustrated in the block diagram shown here.
Figure 4. PCI-DIO24/S functional block diagram
For more information on digital signal connections
For general information about digital signal connections and digital I/O techniques, refer to the Guide to Signal
Connections (available on our web site at
www.mccdaq.com/signals/signals.pdf ).
Caution! Do not connect high current/voltage devices directly to the PCI-DIO24/S or you may damage the
board.
PCI
CONTROLLER
BADR1
Boot
EEPROM
Control
Registers
Decode/Status
Bus
Timing
Controller FPGA and Logic
LOCAL BUS
PCI BUS (5V/3.3V, Universal 32-Bit, 33MHz)
Control
Bus PORT A
PORT A (7:0)
82C55
Interrupt
Control
+5V
IRQ_INPUT
BADR2
Interrupt
IRQ_ENABLE
IRQ_INPUT
IRQ_ENABLE
PORT B (7:0)
PORT CH (3:0)
PORT B
PORT CH
PORT CL
PORT CL (3:0)
37-pin
I/O connector
Control
x 8
x 8
x 4
x 4