PIC18F1220-I/SO Microchip Technology Inc., PIC18F1220-I/SO Datasheet - Page 92

• Manufacturer Part Number: PIC18F1220-I/SO
• Description: Microcontroller; 4 KB Flash; 256 RAM; 256 EEPROM; 16 I/O; 18-Pin-SOIC
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F1220-I/SO

• A/d Inputs: 7-Channel, 10-Bit
• Cpu Speed: 10 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 16
• Interface: USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 18-pin SOIC
• Programmable Memory: 4K Bytes
• Ram Size: 256 Bytes
• Speed: 20 MHz
• Timers: 1-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC18F1220/1320
10.2
PORTB is an 8-bit wide, bidirectional port. The corre-
sponding data direction register is TRISB. Setting a
TRISB bit (= 1) will make the corresponding PORTB
pin an input (i.e., put the corresponding output driver in
a high-impedance mode). Clearing a TRISB bit (= 0)
will make the corresponding PORTB pin an output (i.e.,
put the contents of the output latch on the selected pin).
The Data Latch register (LATB) is also memory
mapped. Read-modify-write operations on the LATB
register read and write the latched output value for
PORTB.
EXAMPLE 10-2:
Pins RB0-RB2 are multiplexed with INT0-INT2; pins
RB0, RB1 and RB4 are multiplexed with A/D inputs;
pins RB1 and RB4 are multiplexed with EUSART; and
pins RB2, RB3, RB6 and RB7 are multiplexed with
ECCP.
Each of the PORTB pins has a weak internal pull-up. A
single control bit can turn on all the pull-ups. This is
performed by clearing bit, RBPU (INTCON2<7>). The
weak pull-up is automatically turned off when the port
pin is configured as an output. The pull-ups are
disabled on a Power-on Reset.
Four of the PORTB pins (RB7:RB4) have an interrupt-
on-change feature. Only pins configured as inputs can
cause this interrupt to occur (i.e., any RB7:RB4 pin
configured as an output is excluded from the interrupt-
on-change comparison). The input pins (of RB7:RB4)
are compared with the old value latched on the last
read of PORTB. The “mismatch” outputs of RB7:RB4
are OR’ed together to generate the RB Port Change
Interrupt with Flag bit, RBIF (INTCON<0>).
DS39605C-page 90
CLRF
CLRF
MOVLW
MOVWF
MOVLW
MOVWF
Note:
PORTB, TRISB and LATB
Registers
PORTB
LATB
0x70
ADCON1 ; digital I/O pins
0xCF
TRISB
On a Power-on Reset, RB4:RB0 are
configured as analog inputs by default and
read as ‘0’; RB7:RB5 are configured as
digital inputs.
; Initialize PORTB by
; clearing output
; data latches
; Alternate method
; to clear output
; data latches
; Set RB0, RB1, RB4 as
;
; initialize data
; direction
; Set RB<3:0> as inputs
; RB<5:4> as outputs
; RB<7:6> as inputs
Value used to
INITIALIZING PORTB
This interrupt can wake the device from Sleep. The
user, in the Interrupt Service Routine, can clear the
interrupt in the following manner:
a)
b)
A mismatch condition will continue to set flag bit, RBIF.
Reading PORTB will end the mismatch condition and
allow flag bit, RBIF, to be cleared.
The interrupt-on-change feature is recommended for
wake-up on key depression operation and operations
where PORTB is only used for the interrupt-on-change
feature. Polling of PORTB is not recommended while
using the interrupt-on-change feature.
FIGURE 10-7:
Note 1:
RBPU
Analog Input Mode
Data Bus
WR LATB
or PORTB
WR TRISB
RD TRISB
RD LATB
RD PORTB
INTx
To A/D Converter
Any read or write of PORTB (except with the
MOVFF instruction). This will end the mismatch
condition.
Clear flag bit, RBIF.
2:
(2)
Schmitt Trigger
Buffer
I/O pins have diode protection to V
To enable weak pull-ups, set the appropriate TRIS
bit(s) and clear the RBPU bit (INTCON2<7>).
Data Latch
TRIS Latch
D
D
CK
CK
BLOCK DIAGRAM OF
RB0/AN4/INT0 PIN
 2004 Microchip Technology Inc.
Q
Q
Q
EN
DD
TTL
Input
Buffer
EN
and V
D
V
SS
P
DD
.
Weak
Pull-up
pin
I/O
(1)