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HC05 Datasheet, PDF (132/232 Pages) Motorola, Inc – High-density complementary metal oxide semiconductor (HCMOS) microcontroller unit
9.2.3 A/D status/control register (ADSTAT)
A/D status/control (ADSTAT)
Address bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
State
on reset
$0009 COCO ADRC ADON 0 CH3 CH2 CH1 CH0 0000 0000
COCO — Conversion complete flag
1 (set)
– COCO is set each time a conversion is complete, allowing the new
result to be read from the A/D result data register ($08). The
converter then starts a new conversion.
0 (clear) – COCO is cleared by reading the result data register or writing to the
status/control register.
Reset clears the COCO flag.
ADRC — A/D RC oscillator control
The ADRC bit allows the user to control the A/D RC oscillator, which is used to provide a
sufficiently high clock rate to the A/D to ensure accuracy when the chip is running at low speeds.
1 (set) – When the ADRC bit is set, the A/D RC oscillator is turned on and, if
ADON is set, the A/D runs from the RC oscillator clock. See Table 9-1.
0 (clear) – When the ADRC bit is cleared, the A/D RC oscillator is turned-off
and, if ADON is set, the A/D runs from the CPU clock.
9
When the A/D RC oscillator is turned on, it takes a time tADRC to stabilize (see Table 12-3). During
this time A/D conversion results may be inaccurate.
Note: If the MCU bus clock falls below 1MHz, the A/D RC oscillator should be switched on.
Power-on or external reset clears the ADRC bit.
Table 9-1 A/D clock selection
ADRC
0
0
1
1
ADON
0
1
0
1
RC
oscillator
OFF
OFF
ON
ON
A/D
converter
Comments
OFF A/D switched off.
ON A/D using CPU clock.
OFF Allows the RC oscillator to stabilize.
ON A/D using RC oscillator clock.
MOTOROLA
9-4
ANALOG TO DIGITAL CONVERTER
MC68HC05X16
Rev. 1