
PIC18F2220/2320/4220/4320
DS39599G-page 112
2007 Microchip Technology Inc.
FIGURE 10-14:
BLOCK DIAGRAM OF
MCLR/VPP/RE3 PIN
MCLR/VPP/
Data Bus
RD PORTE
RD LATE
Schmitt
Trigger
MCLRE
RD TRISE
QD
EN
Latch
Filter
Low-Level
MCLR Detect
High-Voltage Detect
Internal MCLR
HV
RE3
REGISTER 10-1:
TRISE REGISTER
R-0
R/W-0
U-0
R/W-1
IBF
OBF
IBOV
PSPMODE
—
TRISE2
TRISE1
TRISE0
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
IBF: Input Buffer Full Status bit
1 = A word has been received and waiting to be read by the CPU
0 = No word has been received
bit 6
OBF: Output Buffer Full Status bit
1 = The output buffer still holds a previously written word
0 = The output buffer has been read
bit 5
IBOV: Input Buffer Overflow Detect bit (in Microprocessor mode)
1 = A write occurred when a previously input word has not been read (must be cleared in software)
0 = No overflow occurred
bit 4
PSPMODE: Parallel Slave Port Mode Select bit
1 = Parallel Slave Port mode
0 = General Purpose I/O mode
bit 3
Unimplemented: Read as ‘0’
bit 2
TRISE2: RE2 Direction Control bit
1 = Input
0 = Output
bit 1
TRISE1: RE1 Direction Control bit
1 = Input
0 = Output
bit 0
TRISE0: RE0 Direction Control bit
1 = Input
0 = Output