¡ Semiconductor

MSM58321

14

3

Name

Pin No.

Description

READ

READ pin is used to read data; it is activated when it is at the H level. Address

ADDRESS WRITE pins to select the object digit, then an H-level signal is input

to the READ pin to read data.

If a count operation is continued by setting the STOP input to the L level, read

operation must be performed, in principle, while the BUSY output is at the H

level. While the BUSY output is at the L level, count operations are performed

by digit counters and read data is not guaranteed, therefore, read operations are

inhibited in this period. Figure 2 shows a time chart of the BUSY output, 1 Hz

signal inside the IC, and READ input.

A read operation is stopped temporarily within a period of 244 µs from the BUSY

output trailing edge and it is restarted when the BUSY output goes to the H level

again.

If the counter operation is stopped by setting the STOP input to the H level, read

operations are enabled regardless of the BUSY output.

A read operation is enabled by microcomputer software regardless of the BUSY

output during the counter operation by setting the STOP input to the L level.

In this method, read operations are performed two or more times continuously

and data that matches twice is used as guaranteed data.

427 µs

BUSY

1 Hz (inside IC)

Read-enabled

period

The counter inside the IC

starts counting at the

1 Hz signal leading edge.

244 µs

122 µs 61 µs

Read-enabled period

Read operation is enabled in this period:

however, it is used for program switching.

READ input

Read-inhibited period

1 sec

Figure 2

BUSY

1 Hz (inside IC)