PIC16F819T-E Datasheet, PDF (103/176 Pages) Microchip Technology – 18/20-Pin Enhanced Flash Microcontrollers with nanoWatt Technology

12.17 In-Circuit Serial Programming
PIC16F818/819 microcontrollers can be serially
programmed while in the end application circuit. This is
simply done with two lines for clock and data and three
other lines for power, ground and the programming
voltage (see Figure 12-10 for an example). This allows
customers to manufacture boards with unprogrammed
devices and then program the microcontroller just
before shipping the product. This also allows the most
recent firmware or a custom firmware to be
programmed.
For more information on serial programming, please refer
to the “PIC16F818/819 Flash Memory Programming
Specification” (DS39603).
Note:
The Timer1 oscillator shares the T1OSI
and T1OSO pins with the PGD and PGC
pins used for programming and
debugging.
When using the Timer1 oscillator, In-Circuit
Serial Programming™ (ICSP™) may not
function correctly (high voltage or low
voltage) or the In-Circuit Debugger (ICD)
may not communicate with the controller.
As a result of using either ICSP or ICD, the
Timer1 crystal may be damaged.
If ICSP or ICD operations are required, the
crystal should be disconnected from the
circuit (disconnect either lead) or installed
after programming. The oscillator loading
capacitors may remain in-circuit during
ICSP or ICD operation.
PIC16F818/819
FIGURE 12-10:
TYPICAL IN-CIRCUIT
SERIAL PROGRAMMING
CONNECTION
External
Connector
Signals
To Normal
Connections
*
PIC16F818/819
+5V
VDD
0V
VSS
VPP
MCLR/VPP
CLK
Data I/O
RB3/PGM
RB6
RB7
RB3^†
***
VDD
To Normal
Connections
* Isolation devices (as required).
† _{RB3 only used in LVP mode.}
 2004 Microchip Technology Inc.
DS39598E-page 101