ICSP: In-Circuit Serial Programming

In-System Programming (ISP) is a technique where a programmable device is programmed after the device is placed in a circuit board. In-Circuit Serial Programming (ICSP) is an enhanced ISP technique. ICSP (In-Circuit Serial Programming) mode is special programming protocols that allow read and write to PIC Microcontroller and is the most direct method used to program the device. The ICSP capability is microchip’s proprietary process for microcontroller programming in the target application. The ICSP interface uses two pins as its core. The programming data pin (PGD) functions as both an input and an output, allowing programming data to be read in and device information to be read out on command. The programming clock pin (PGC) clocks in data and controls the overall process.

Serial programming allows customers to manufacture boards with unprogrammed devices and then to program the digital signal controller just before shipping the product. Serial programming also allows the most recent firmware or a custom firmware to be programmed.

Figure 19: ICSP Connector

PGD - Data: usual port and connection RB7

PGC - Clock: usual port and connection RB6

RESET: for the reset input

These are the signals that do the work. Data (PGD) and clock (PGC) transmit data to the pic micro. First data is sent either high or low voltage (0/1). After a suitable time the clock is strobe low to high - rising edge clocking the data into the microcontroller. PGD is also the line driven by the pic micro during verify i.e. it is bi-directional.