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Base address – Measurement Computing CIO-DIO24/CTR3 User Manual

Page 9

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CIO-DIO24/CTR3 User's Guide

Installing the CIO-DIO24/CTR3

The CIO-DIO24/CTR3 is shipped with the factory-default settings listed in the table below.

Factory-configured default settings

Switch/jumper Description

Default

setting

Base address DIP switches

Sets the base address

300h (768 decimal)

Interrupt level jumper

Sets the interrupt level

"X" position (no interrupt level set)

Wait state jumper

Enables/disables the on-board wait-state

generator.

Off (disabled)

Clock source jumpers

Sets the input signal for each counter

Not set

Review the following information to change the default configuration of a switch or jumper.

Base address

The easiest way to set the base address is to let InstaCal show you the correct settings. However, if you are

already familiar with setting ISA base addresses, you may use the base address switch description below to

guide your base address selection.

Each I/O board uses one or more I/O address locations within your computer’s I/O address space. To avoid

interference with other installed boards, each board must use unique addresses. The base address is the board’s

starting location that software writes to when communicating with the CIO-DIO24/CTR3. A set of DIP

switches is used to set the base address. By placing the switch down, the CIO-DIO24/CTR3 address decode

logic is instructed to respond to that address bit. A complete address is constructed by calculating the HEX or

decimal number which corresponds to all the address bits the board has been instructed to respond to.

The board is shipped with the base address set to 300 hex (see

)

. Unless there is already a board in your

system that uses address 300 hex (768 decimal), leave the switches as they were set at the factory.

Figure 2

Figure 2. Base address switch

SW
A9
A8
A7
A6
A5
A4
A3

HEX
200
100
80
40
20
10
08

9

8

7

6

5

4

3

In the default configuration, addresses 9 and 8 are down, and all others are up. Address 9

= 200 hex

(512 decimal), and address 8 = 100 hex (256 decimal). When added together they equal 300 hex (768 decimal).

Disregard the numbers printed on the switch
When setting the base address, refer to the numbers printed in white on the printed circuit board.

Certain addresses are used by the computer. Other addresses are free, and may be used by the CIO-

DIO24/CTR3. Refer to the following table for a list of I/O addresses.

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