µPD4701A

5

3. SWITCH INPUT OPERATION

The

µPD4701A can process up to 3 contact points as switch inputs (active-“L” input). Switch input is read as part

of the count data upper byte together with the switch flag status as an internal status (see Fig. 3). These are all active-

“H” outputs. The switch flag status, SF, is equivalent to the switch flag output, SF, described below.

Fig. 3 Data Output Format

7

SF

6

L

5

R

4

M

3

2

1

0

7

6

5

4

3

2

1

0

Bit No.

Upper Byte

Bit No.

Lower Byte

SF : Switch Flag

L : Left Switch

R : Right Switch

M : Middle Switch

4. OPERATION OF SWITCH FLAG, SF

The switch flag, SF, becomes active (active-“L” output) when the RIGHT, LEFT or MIDDLE switch input is “L”.

SF can also be read as the switch flag status together with the count data.

5. DATA READ OPERATION

The CPU reads the count data and switch input status by controlling CS, X/Y and U/L. The relation between these

is shown in Table 1. (At this time, the data latched on the falling edge of CS is output. If X/Y or U/L is switched while

CS is still “L”, the data at the point at which CS changes from “H” to “L” is read. When CS is set to “H”, new data is

read into the latch, and the new data is confirmed on the next fall of CS.

Table 1 Data Output Table

CS

X/Y

U/L

000

X

001

SF

L

R

M

X

X

X

010

Y

011

SF

L

R

M

Y

Y

Y

1

××

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