UPD784938 Datasheet, PDF (420/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 16 A/D CONVERTER
16.4.5 A/D conversion operation start by hardware
An A/D conversion operation start by hardware is made possible by setting both the TRG bit and the CS bit of the
A/D converter mode register (ADM) to 1. When the TRG bit and the CS bit of the ADM are both set to 1, external signals
are placed in the standby state, and an A/D conversion operation is started when a valid edge is input to the INTP5 pin
(P26 pin).
If another valid edge is input to the INTP5 pin after the A/D conversion operation has been started by a valid edge input
to the INTP5 pin, the A/D conversion operation being performed at that time is suspended, and A/D conversion is performed
from the beginning in accordance with the contents set in the ADM.
If a value is written to the ADM during an A/D conversion operation (CS bit = 1) such that the TRG bit and CS bit are
both set to 1 again, the A/D conversion operation being performed at that time is suspended (the standby state is also
suspended), and a standby state is entered in which the A/D converter waits for input of a valid edge to the INTP5 pin in
the A/D conversion operation mode in accordance with the written value, and a conversion operation is started when a valid
edge is input.
Use of this function allows A/D conversion operations to be synchronized with external signals. Once A/D conversion
operation is started, as soon as one A/D conversion operation ends the next A/D conversion operation is started in
accordance with the operation mode set by the ADM (the A/D converter does not wait for INTP5 pin input), and conversion
operations continue repeatedly until an instruction that writes to the ADM is executed, or a valid edge is input to the INTP5
pin.
Caution Approximately 10 µs is required from the time a valid edge is input to the INTP5 pin until the A/D
conversion operation is actually started. This delay must be taken into account in the design stage.
See CHAPTER 22 EDGE DETECTION FUNCTION for details of the edge detection function.
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Preliminary User’s Manual U13987EJ1V0UM00