
Technical Data
MC68HC11E Family
—
Rev. 4
214
Analog-to-Digital (A/D) Converter
MOTOROLA
Analog-to-Digital (A/D) Converter
10.4 A/D Converter Power-Up and Clock Select
Bit 7 of the OPTION register controls A/D converter power-up. Clearing
ADPU removes power from and disables the A/D converter system.
Setting ADPU enables the A/D converter system. Stabilization of the
analog bias voltages requires a delay of as much as 100
μ
s after turning
on the A/D converter. When the A/D converter system is operating with
the MCU E clock, all switching and comparator operations are inherently
synchronized to the main MCU clocks. This allows the comparator
output to be sampled at relatively quiet times during MCU clock cycles.
Since the internal RC oscillator is asynchronous to the MCU clock, there
is more error attributable to internal system clock noise. A/D converter
accuracy is reduced slightly while the internal RC oscillator is being used
(CSEL = 1).
ADPU
—
A/D Power-Up Bit
0 = A/D powered down
1 = A/D powered up
CSEL
—
Clock Select Bit
0 = A/D and EEPROM use system E clock.
1 = A/D and EEPROM use internal RC clock.
IRQE
—
Configure IRQ for Edge-Sensitive Only Operation
Refer to
Section 5. Resets and Interrupts
.
Address:
$1039
Bit 7
6
5
4
3
2
1
Bit 0
Read:
ADPU
CSEL
IRQE
(1)
DLY
(1)
CME
CR1
(1)
CR0
(1)
Write:
Reset:
0
0
0
1
0
0
0
0
1. Can be written only once in first 64 cycles out of reset in normal modes or at any time in special modes
= Unimplemented
Figure 10-4. System Configuration Options Register (OPTION)