2003 Microchip Technology Inc.
DS39582B-page 7
PIC16F87XA
FIGURE 1-2:
PIC16F874A/877A BLOCK DIAGRAM
13
Data Bus
8
14
Program
Bus
Instruction reg
Program Counter
8 Level Stack
(13-bit)
RAM
File
Registers
Direct Addr
7
RAM Addr
(1)
9
Addr MUX
Indirect
Addr
FSR reg
Status reg
MUX
ALU
W reg
Power-up
Timer
Oscillator
Start-up Timer
Power-on
Reset
Watchdog
Timer
Instruction
Decode &
Control
Timing
Generation
OSC1/CLKI
OSC2/CLKO
MCLR
V
DD
, V
SS
PORTA
PORTB
PORTC
PORTD
PORTE
RA4/T0CKI/C1OUT
RA5/AN4/SS/C2OUT
RC0/T1OSO/T1CKI
RC1/T1OSI/CCP2
RC2/CCP1
RC3/SCK/SCL
RC4/SDI/SDA
RC5/SDO
RC6/TX/CK
RC7/RX/DT
RE0/RD/AN5
RE1/WR/AN6
RE2/CS/AN7
8
8
Brown-out
Reset
Note 1: Higher order bits are from the Status register.
RA3/AN3/V
REF
+
RA2/AN2/V
REF
-/CV
REF
RA1/AN1
RA0/AN0
Parallel
8
3
RB0/INT
RB1
RB2
RB3/PGM
RB4
RB5
RB6/PGC
RB7/PGD
In-Circuit
Debugger
Low-Voltage
Programming
RD0/PSP0
RD1/PSP1
RD2/PSP2
RD3/PSP3
RD4/PSP4
RD5/PSP5
RD6/PSP6
RD7/PSP7
USART
CCP1,2
Synchronous
10-bit A/D
Timer0
Timer1
Timer2
Serial Port
Data EEPROM
Comparator
Voltage
Reference
Device
Program Flash
Data Memory
Data EEPROM
PIC16F874A
4K words
192 Bytes
128 Bytes
PIC16F877A
8K words
368 Bytes
256 Bytes
Flash
Program
Memory
Slave Port
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