PIC24FJ128GA Datasheet, PDF (163/232 Pages) Microchip Technology – General Purpose, 16-Bit Flash Microcontrollers

PIC24FJ128GA FAMILY
19.0 PROGRAMMABLE CYCLIC
REDUNDANCY CHECK (CRC)
GENERATOR
The programmable CRC generator offers the following
features:
• User-programmable polynomial CRC equation
• Interrupt output
• Data FIFO
19.1 Registers
There are four registers used to control programmable
CRC operation:
• CRCCON
• CRCXOR
• CRCDAT
• CRCWDAT
REGISTER 19-1: CRCCON: CRC CONTROL REGISTER
Upper Byte:
U-0
U-0
—
—
bit 15
R/W-0
CSIDL
R-0
R-0
R-0
R-0
R-0
VWORD4 VWORD3 VWORD2 VWORD1 VWORD0
bit 8
Lower Byte:
R-0
R-1
U-0
CRCFUL CRCMPT
—
bit 7
R/W-0
CRCGO
R/W-0
PLEN3
R/W-0
PLEN2
R/W-0
PLEN1
R/W-0
PLEN0
bit 0
bit 15-14 Unimplemented: Read as ‘0’
bit 13 CSIDL: CRC Stop in Idle Mode bit
1 = Discontinue module operation when device enters Idle mode
0 = Continue module operation in Idle mode
bit 12-8 VWORD4:VWORD0: Pointer Value bits
Indicates the number of valid words in the FIFO. Has a maximum value of 8 when PLEN3:PLEN0 > 7,
or 16 when PLEN3:PLEN0 ≤ 7.
bit 7
CRCFUL: FIFO Full bit
1 = FIFO is full
0 = FIFO is not full
bit 6
CRCMPT: FIFO Empty Bit
1 = FIFO is empty
0 = FIFO is not empty
bit 5
Unimplemented: Read as ‘0’
bit 4
CRCGO: Start CRC bit
1 = Start CRC serial shifter
0 = CRC serial shifter turned off
bit 3-0 PLEN3:PLEN0: Polynomial Length bits
Denotes the length of the polynomial to be generated minus 1.
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
© 2006 Microchip Technology Inc.
Preliminary
DS39747C-page 161