7480 datasheet(38/98 Pages) RENESAS

38 / 98 page

MITSUBISHI MICROCOMPUTERS

7480/7481 GROUP

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

PRELIMINAR

Notice:

This

is not

a final

specification.

Some

parametric

limits

are

subject

to change.

A-D Converter

For A-D conversion, the 8-bit successive comparison method is

used. Figure 38 shows a block diagram of A-D conversion. Con-

version is automatically performed once started by the program.

There are 8 analog input pins that are in common with P27 to P20

of port P2 (4 pins of P23 to P20 in the 7480 group).

Pin inputs to be A-D converted are selected by bit 2 to bit 0 of the

A-D control register (address 00D916). Bit 3 of the A-D control reg-

ister is an A-D conversion completion bit. This bit is “0” during A-D

conversion and “1” after completion of it. Accordingly, it is possible

by checking this bit to know whether A-D conversion is completed

or not. Figure 39 shows the relationship between the contents of

the A-D control register and input pins to be selected.

The A-D conversion register (address 00DA16) stores conversion

results, so it is possible to know them by reading the contents of

this register.

Next, the procedure for executing A-D conversion will be ex-

plained below. First, set values in bit 2 to bit 0 of the A-D control

Next, clear the A-D conversion completion bit to “0”. With this write

operation, A-D conversion is started. The A-D conversion is com-

pleted after the lapse of 50 machine cycles (12.5

µs at f(XIN)= 8

MHz), and the A-D conversion completion bit is set to “1”. The A-D

conversion interrupt request bit is also set to “1”. Conversion re-

sults are stored in the A-D conversion register.

Fig. 38 Block diagram of A-D converter circuit

Comparator

A-D control circuit

A-D conversion register

(address 00DA16)

Switch tree

Ladder resistor

A-D conversion

completion

interrupt request

VSS (Note 1)

VREF

1 : AVSS for the 44P6N package of the 7481 group.

2 : The 7480 group is not provided with P2 4/IN4 to P27/IN7.

P20/IN0

P21/IN1

P22/IN2

P23/IN3

P24/IN4

P25/IN5

P26/IN6

P27/IN7

Data bus

A-D control register

(address 00D916)

Notes

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