User`s guide

ManualsBrandsAcces ManualsComputer equipmentPCI-DIO-24H

5.4 INPUT PORTS

In 82C55 mode 0 configuration, ports configured for input read the state of the input

lines at the moment the read is executed, transitions are not latched.

For information on modes 1 (strobed I/O) and 2 (bi-directional strobed I/O), you will

need to acquire an Intel or AMD data book and see the 82C55 data sheet.

Group BGroup A

CLBM1CUAM2M3MS

01234567

The 82C55 may be programmed to operate in Input/ Output (mode 0), Strobed Input/

Output (mode 1) or Bi-Directional Bus (mode 2).

NOTE!

Only 82C55 mode 0 is available on the PCI-DIO24H &

24H/CTR3.

Included here is information on programming the 82C55 in mode 0. Those wishing

to use the 82C55 in modes 1 or 2, or who wish to program the 82C54 counter on the

PCI-DIO24H/CTR3, must procure a data book from Intel Corporation Literature

Department.

When the PC is powered up or RESET, the 82C55 is reset. This places all 24 lines in

Input mode and no further programming is needed to use the 24 lines as TTL inputs.

To program the 82C55 for other modes, the following control code byte must be

assembled into an 8 bit byte.

MS = Mode Set. 1 = mode set active

Output0000

Input1111

Independent FunctionCHCLBA

Bi-Directional BusMode 2X1

Strobed Input/OutputMode 110

Input/OutputMode 000

Group A FunctionM2M3

M1 = 0 is mode 0 for group B. Input / Output

M1 = 1 is mode 1 for group B. Strobed Input / Output

The Ports A, B, C High and C Low may be independently programmed for input or

output.

3.4 COUNTER CONNECTIONS & SETUP

3.4.1 1 or 10 MHz Time Base

The user has the option of setting the onboard crystal time base to 1 MHz or 10 MHz.

This selection is made during the InstaCAL board setup. The time base defaults to 10

MHz.

3.4.2 Onboard counter interconnect jumpers

For the convenience of those users who wish to make (pseudo) permanent connec-

tions among the counter channels, the board has been configured with three jumper

locations. When installed, these jumpers can make the connections shown below:

Please note, that all of these connections can be made via the standard 37-Pin I/O

connector, and the jumpers have been included as a convenience only.

Jumper positions are provided to connect:

• Timebase

output

and Counter 0

Clk

• Counter 0

output

and Counter 1

Clk

• Counter 1

output

and Counter 2

Clk