PIC16F676-I Datasheet, PDF (44/132 Pages) Microchip Technology – 14-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F630/676
REGISTER 6-2:
VRCON — VOLTAGE REFERENCE CONTROL REGISTER (ADDRESS: 99h)
R/W-0
U-0
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
VREN
—
VRR
—
VR3
VR2
VR1
VR0
bit 7
bit 0
bit 7
bit 6
bit 5
bit 4
bit 3-0
VREN: CVREF Enable bit
1 = CVREF circuit powered on
0 = CVREF circuit powered down, no IDD drain
Unimplemented: Read as ‘0’
VRR: CVREF Range Selection bit
1 = Low range
0 = High range
Unimplemented: Read as ‘0’
VR3:VR0: CVREF value selection bits 0  VR [3:0]  15
When VRR = 1: CVREF = (VR3:VR0 / 24) * VDD
When VRR = 0: CVREF = VDD/4 + (VR3:VR0 / 32) * VDD
Legend:
R = Readable bit
- n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
6.9 Comparator Interrupts
The comparator interrupt flag is set whenever there is
a change in the output value of the comparator.
Software will need to maintain information about the
status of the output bits, as read from CMCON<6>, to
determine the actual change that has occurred. The
CMIF bit, PIR1<3>, is the comparator interrupt flag.
This bit must be reset in software by clearing it to ‘0’.
Since it is also possible to write a ‘1’ to this register, a
simulated interrupt may be initiated.
The CMIE bit (PIE1<3>) and the PEIE bit
(INTCON<6>) must be set to enable the interrupt. In
addition, the GIE bit must also be set. If any of these
bits are cleared, the interrupt is not enabled, though the
CMIF bit will still be set if an interrupt condition occurs.
The user, in the Interrupt Service Routine, can clear the
interrupt in the following manner:
a) Any read or write of CMCON. This will end the
mismatch condition.
b) Clear flag bit CMIF.
A mismatch condition will continue to set flag bit CMIF.
Reading CMCON will end the mismatch condition and
allow flag bit CMIF to be cleared.
Note:
If a change in the CMCON register (COUT)
should occur when a read operation is
being executed (start of the Q2 cycle), then
the CMIF (PIR1<3>) interrupt flag may not
get set.
TABLE 6-2: REGISTERS ASSOCIATED WITH COMPARATOR MODULE
Address Name Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOD
Value on
all other
Resets
0Bh/8Bh
0Ch
19h
8Ch
85h
99h
Legend:
INTCON GIE PEIE T0IE INTE RAIE T0IF INTF RAIF 0000 0000 0000 000u
PIR1
EEIF ADIF
—
—
CMIF
—
— TMR1IF 00-- 0--0 00-- 0--0
CMCON —
COUT
—
CINV
CIS
CM2 CM1 CM0 -0-0 0000 -0-0 0000
PIE1
EEIE ADIE
—
—
CMIE
—
— TMR1IE 00-- 0--0 00-- 0--0
TRISA
—
— TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 --11 1111 --11 1111
VRCON VREN —
VRR
—
VR3
VR2
VR1
VR0 0-0- 0000 0-0- 0000
x = unknown, u = unchanged, – = unimplemented, read as ‘0’. Shaded cells are not used by the comparator module.
DS40039F-page 44
 2010 Microchip Technology Inc.