XC68HC705JJ7 Motorola, XC68HC705JJ7 Datasheet - Page 136

• Manufacturer Part Number: XC68HC705JJ7
• Description: MICROCONTROLLER
• Manufacturer: Motorola

Analog Subsystem
8.7.2.2 External Ratiometric Reference
8.8 Voltage Comparator Features
8.8.1 Voltage Comparator 1
Advance Information
136
If readings are to be ratiometric to some external source, the reference
measurement point can be connected to any one of the channel selected
pins from PB1–PB4. In this case, the reference reading can be taken by
setting the MUX bit in the AMUX which connects channel selection bus
to the pin connected to the external reference source. If the external
reference is greater than V
used to select the 1/2 divided input.
The two internal comparators can be used as simple voltage
comparators if set up as described in
be active in the wait mode and can directly restart the part by means of
the analog interrupt. Both comparators can also be active in the stop
mode, but cannot directly restart the part. However, the comparators can
directly drive PB4 which can then be connected externally to activate
either a port interrupt on the PA0:3 pins or the IRQ/V
Voltage comparator 1 is always connected to two of the port B I/O pins.
These pins should be configured as inputs and have their software
programmable pulldowns disabled. Also, the negative input of voltage
comparator 1 is connected to the PB3/AN3/TCAP and shared with the
input capture function of the 16-bit programmable timer. Therefore, the
timer input capture interrupt should be disabled so that changes in the
Comparator
1
2
Table 8-8. Voltage Comparator Setup Conditions
ISEN = 0
Current
affected
Source
Enable
Not
Analog Subsystem
Discharge
ISEN = 0
Disable
affected
Device
Not
DD
–1.5 volts, then the DHOLD bit should be
MC68HC705JJ7 • MC68HC705JP7 — REV 4
DDRB2 = 0
DDRB3 = 0
DDRB0 = 0
DDRB1 = 0
Port B Pin
as Inputs
Table
8-8. Both comparators can
Pulldowns
Port B Pin
PDIB2 = 1
PDIB3 = 1
PDIB0 = 1
PDIB1 = 1
Disabled
PP
pin.
Prog. Timer
IEDG = 1
ICEN = 0
Capture
affected
Source
MOTOROLA
Input
Not