UPD17P136ACT datasheet(157/292 Pages) NEC

157 / 292 page

CHAPTER 13 PERIPHERAL HARDWARE

138

Table 13-1. Data Conversion Time for the A/D Converter

Note Includes GET instruction to read data from ADCR.

(2) Single Mode

(a) Overview of single mode

In the single mode, data in the 8-bit data register (ADCR) is compared with voltage subjected to D/A

conversion and with an analog input signal from a pin.

The comparison result appears in the ADCCMP flag.

(b) Explanation of single mode operation

If ADCSOFT is 1, the A/D converter function enters the single mode.

Before single mode operation starts, port input is disabled for the pin to be used for analog input by setting

P0CnIDI to 1. (This is done for the same reason as in the successive mode.)

To start single mode operation, execute a write instruction (PUT ADCR, DBF) for the 8-bit data register

(ADCR) when ADCSOFT is 1.

The comparison result in single mode appears in ADCCMP at the execution of the third instruction after

a PUT instruction is executed to write to the 8-bit data register (ADCR). At this time, the ADCEND flag

becomes undefined.

Bits for which A/D conversion is

completed (valid bits when ADCR is read)

Most significant bit

High-order 2 bits

High-order 3 bits

High-order 4 bits

High-order 5 bits

High-order 6 bits

High-order 7 bits

All 8 bits

Number of instructions

executed after

ADCSTRT is set to 1Note

4 instructions

7 instructions

10 instructions

13 instructions

16 instructions

19 instructions

22 instructions

25 instructions

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