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Analog-to-Digital Converter
ADC Setup Examples
MN102H75K/F75K/85K/F85K LSI User Manual Panasonic Semiconductor Development Company
149
Panasonic
■ To set up the input port:
Set the P0DIR[5:3] bits of the port 0 I/O control register (P0DIR) to 0. This sets
the ADIN2 (P05), ADIN1 (P04), and ADIN0 (P03) pins (P11) to general-purpose
input.
■
To set up the ADC:
Set the operating conditions in the ADC control register (ANCTR). Select
multiple-channel, single-conversion mode (ANMD[1:0] = b’01’) and B
OSC
/8 as
the clock source (ANCK[1:0] = b’10’). Set the conversion start/busy bit, ANEN,
to 0. Set ANTC to 1, enabling conversion start at timer 1 underflow. Set the
AN1CH[3:0] field to the first channel (channel 0) and set the ANNCH[3:0] to the
last channel (channel 2).
ANCTR (example) x’00FDA0’
■ To set up the conversion cycle
1. Set the divide-by ratio for timer 1. To divide B
OSC
/4 by 256, write 255
(x’FF’) to the timer 1 base register (TM1BR). (The valid range for TM1BR
is 1 to 255.)
TM1BR (example) x’00FE11’
Do not change the clock source
once you have selected it.
Selecting the clock source while
you set up the count operation
control will corrupt the value in
the binary counter.
2. Set the TM1LD bit of the TM1MD register to 1 and the TM1EN bit to 0.
(This loads the value in the base register to the binary counter.)
TM1MD (example) x’00FE21’
3. Set TM1LD to 0 and TM1EN to 1. This starts the timer. Counting begins at
the start of the next cycle.
When the binary counter (TM1BC) reaches 0, the microcontroller reloads the
value in the base register (TM1BR) to TM1BC and simultaneously generates a
timer 1 underflow interrupt. After each timer 1 underflow, the ADC converts
each of the ADIN[2:0] inputs a single time.
Bit:1514131211109876543210
AN
NCH3
AN
NCH2
AN
NCH1
AN
NCH0
AN
1CH3
AN
1CH2
AN
1CH1
AN
1CH0
AN
EN
AN
TC
——
AN
CK1
AN
CK0
AN
MD1
AN
MD0
Setting:0010000001001001
Bit:76543210
TM1
BR7
TM1
BR6
TM1
BR5
TM1
BR4
TM1
BR3
TM1
BR2
TM1
BR1
TM1
BR0
Setting:11111111
Bit:76543210
TM1
EN
TM1
LD
————
TM1
S1
TM1
S0
Setting:01000010