5

HS-54C138RH

Typical applications include systems which require multiple

input/output ports and memories. When the HS-54C138RH

is enabled one of the eight outputs will go low. This output

can be used to select a particular device or a group of

devices. The HS-54C138RH can also be cascaded to

provide an enabling scheme for larger systems and allow

one decoder to control eight other decoders as in Figure 1.

Figure 2 shows a configuration that can be used to enable

multiple I/O ports or memory devices. Up to 24 memory

devices or I/O ports can be controlled using this circuit.

For demultiplexer operation, one of the three enable inputs is

used as the data input while the other two inputs are enable.

The transmitted data is distributed to the proper output as

determined by the 3-line select inputs. See Figure 3.

FIGURE 1

FIGURE 2

FIGURE 3

Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0

SELECT A

ENABLE

HS-54C138RH

Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0

HS-54C138RH

Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0

HS-54C138RH

Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0

HS-54C138RH

“0”

“1”

“0”

“1”

“0”

“1”

TO OTHER

DEVICES

SELECT B

ENABLE

ENABLE

ENABLE

Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0

G1 G2B G2A

C

B

A

Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0

G1 G2B G2A

C

B

A

Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0

G1 G2B G2A

C

B

A

EN

EN

EN A4

A3

A2 A1 A0

PORT NUMBERS OR CHIP SELECTS

Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0

G1 G2B G2A

C

B

A

DATA

INPUT

EN

EN

Spec Number

518053