E CLOCK
MSB
4
CYCLES
BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 LSB
2
2
2
2
2
2
2
2
CYC
12 E CYCLES
CYC CYC CYC CYC CYC CYC CYC END
SAMPLE ANALOG INPUT
SUCCESSIVE APPROXIMATION SEQUENCE
CONVERT FIRST
CONVERT SECOND
CHANNEL, UPDATE
ADR2
CONVERT THIRD
CHANNEL, UPDATE
ADR3
CONVERT FOURTH
CHANNEL, UPDATE
ADR4
CHANNEL, UPDATE
ADR1
0
32
64
96
128 — E CYCLES
A/D CONVERSION TIM
Figure 14 A/D Conversion Sequence
DIFFUSION/POLY
COUPLER
ANALOG
INPUT
PIN
*
+ ~20V
– ~0.7V
+ ~12V
– ~0.7V
≤ 4 KΩ
< 2 pF
~ 20 pF
400 nA
JUNCTION
LEAKAGE
DAC
CAPACITANCE
DUMMY N-CHANNEL
OUTPUT DEVICE
INPUT
PROTECTION
DEVICE
V
RL
* THIS ANALOG SWITCH IS CLOSED ONLY DURING THE 12-CYCLE SAMPLE TIME.
ANALOG INPUT PIN
Figure 15 Electrical Model of an Analog Input Pin (Sample Mode)
ADCTL — A/D Control/Status
$1030
Bit 7
CCF
U
6
0
0
5
SCAN
U
4
MULT
U
3
CD
U
2
CC
U
1
CB
U
Bit 0
CA
U
RESET:
CCF — Conversions Complete Flag
Set after an A/D conversion cycle. Cleared when ADCTL is written.
SCAN — Continuous Scan Control
0 = Do four conversions and stop
1 = Convert four channels in selected group continuously
MULT — Multiple Channel/Single Channel Control
0 = Convert single channel selected
1 = Convert four channels in selected group
MOTOROLA
42
MC68HC11A8
MC68HC11A8TS/D
MOTOROLA [ MOTOROLA ]
