CLC018 datasheet(9/18 Pages) NSC

9 / 18 page

Operation (Continued)

put address (OA) bus. Data to be written into the load regis-

ter, consisting of the 3-bit address of the input to be con-

nected to that output and the output-enable control bit, are

placed on the input address (IA) bus. Input data is stored in

the load registers at the low-to-high transition of the LOAD

input pin with chip-select (CS) high-true. The contents of the

load registers are transferred to the second rank of CON-

FIGURATION REGISTERS at the low-to-high transition of

the CNFG input signal (with CS high). This causes the state

of the entire switch matrix to be set to the selected configu-

ration.

The entire crosspoint may be placed in an initializing state,

with all outputs connected to input-0 and with all outputs ei-

ther enabled or TRI-STATE. To do so, hold TRI low to make

outputs active, or high to place outputs in TRI-STATE, and

apply a high-going pulse to the RES input pin (with CS high).

In summary, outputs are configured by:

first placing the 3-bit address of that output on the OA

bus together with

the 3-bit address of the input to be connected to that

output on the IA bus,

the output-enable (TRI-STATE) control bit for that output

on the IA bus,

making chip-select (CS) true, and then

providing a high-going pulse to the LOAD input pin.

Repeat these four steps for each output to be config-

ured.

The entire crosspoint matrix may now be configured with the

data held in the load registers. To implement the configura-

tion, apply a high-going pulse to the CNFG input pin. The

contents of the load registers are transferred to the configu-

ration registers and the new configuration of all crosspoints

is effected.

The CLC018 Configuration Truth Table is shown at the end

of the datasheet.

EXPANDING THE SWITCH SIZE

The CLC018 was designed for easy expansion to larger ar-

ray sizes without paying a significant penalty in either speed

or power. The power dissipation of the expanded array will

be dominated by the number of active outputs, therefore

power will increase linearly with the array size even though

the number of components required increases as the square

of the array size. As an example, a single CLC018 can be

used for an 8x8 array, and it will dissipate about 0.85W. A 32

x 32 array will require 16 CLC018s and will consume only

about 4W.

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