PIC16F628-20P Datasheet, PDF (39/170 Pages) Microchip Technology – FLASH-Based 8-Bit CMOS Microcontroller

FIGURE 5-12:
RBPU
BLOCK DIAGRAM OF RB4/PGM PIN
Data Bus
WR PORTB
WR TRISB
RD TRISB
LVP
RD PORTB
PGM input
D
Q
CK Q
Data Latch
D
Q
CK Q
TRIS Latch
Schmitt
Trigger
Set RBIF
From other
RB<7:4> pins
PIC16F62X
VDD
P _{weak pull-up}
VDD
RB4/PGM
VSS
TTL
input
buffer
Q
D
EN
Q1
Q
D
Q3
EN
Note 1: The low voltage programming disables the interrupt-on-change and the weak pull-ups on RB4.
 2003 Microchip Technology Inc.
Preliminary
DS40300C-page 37