Chapter 14 8/10-Bit A/D Converter; Overview - Fujitsu MB91260B Series Hardware Manual

CHAPTER 14 8/10-BIT A/D CONVERTER

14.1

Overview

The 8/10-bit A/D converter has a feature to convert analog input voltage to a 10 or 8-bit
digital value, using the RC successive comparison/conversion method. The input signal
can be selected from 8 channels of analog input pin, and three types of conversions can
be activated: software, internal clock, and external pin trigger.
■ Function of 8/10-bit A/D Converter
There is an A/D conversion feature to convert analog voltage (input voltage) input to the analog input pins
into digital values. This feature has the following benefits.
• The conversion time is a minimum of 1.2 µs (including the sampling time using the 33 MHz machine
clock).
• The conversion method used is the RC successive comparison conversion method with sample hold
circuit.
• A resolution of 10- or 8-bit can be selected.
• The analog input pin can be selected from the 8 channels using the program.
• After A/D conversion is completed, an interrupt request can be generated.
• No data are lost in the interrupt enable status since the conversion data protection function works even
in the continuous conversion.
• One of the following conversion activation causes can be selected: software, 16-bit reload timer 1 or
multifunctional timer (rising edge), or external pin triggers (falling edge).
There are three conversion modes.
Table 14.1-1 Conversion Modes of 8/10-bit A/D Converter
Conversion Mode
Single conversion
mode
Continuous
conversion mode
Pause-conversion
mode
• This model has three units: Unit 0, which has 8 analog-input channels; and units 1 and 2, which have
two analog-input channels.
• The unit-0 activation trigger is the OR of the reload timer 1 and multifunctional timer. Operate reload
timer 1 when activation via the multifunctional timer is enabled to activate A/D unit 0 via both
activation triggers.
324
Single Conversion Operation
The specified channel (one
channel only) is converted for one
time and terminated.
Repeatedly convert specified
channel (1 channel only).
The specified channel (one
channel only) is converted for one
time and suspended until the next
start.
Scanning Conversion Operation
Continuous plural channels (maximum 8
channels can be specified) are converted for
one time and terminated.
Repeatedly convert multiple channels (up
to 8 can be specified) in succession.
Continuous plural channels (maximum 8
channels can be specified) are converted.
However, one channel is converted and
suspended until the next start.