ST72344K2 datasheet(28/247 Pages) STMICROELECTRONICS

28 / 247 page

Flash program memory

ST72344xx, ST2345xx

28/247

Doc ID 12321 Rev 6

4.3.1

In-circuit programming (ICP)

ICP uses a protocol called ICC (in-circuit communication) which allows an ST7 plugged on a

printed circuit board (PCB) to communicate with an external programming device connected

via cable. ICP is performed in three steps:

Switch the ST7 to ICC mode (in-circuit communications). This is done by driving a specific

signal sequence on the ICCCLK/DATA pins while the RESET pin is pulled low. When the

ST7 enters ICC mode, it fetches a specific reset vector which points to the ST7 System

Memory containing the ICC protocol routine. This routine enables the ST7 to receive bytes

from the ICC interface.

●

Download ICP Driver code in RAM from the ICCDATA pin

●

Execute ICP Driver code in RAM to program the Flash memory

Depending on the ICP Driver code downloaded in RAM, Flash memory programming can

be fully customized (number of bytes to program, program locations, or selection of the

serial communication interface for downloading).

4.3.2

In-application programming (IAP)

This mode uses an IAP Driver program previously programmed in Sector 0 by the user (in

ICP mode).

This mode is fully controlled by user software. This allows it to be adapted to the user

application (user-defined strategy for entering programming mode, choice of

communications protocol used to fetch the data to be stored etc.)

IAP mode can be used to program any memory areas except Sector 0, which is write/erase

protected to allow recovery in case errors occur during the programming operation.

4.4

ICC interface

ICP needs a minimum of 4 and up to 7 pins to be connected to the programming tool. These

pins are:

●

RESET: device reset

●

VSS: device power supply ground

●

ICCCLK: ICC output serial clock pin

●

ICCDATA: ICC input serial data pin

●

ICCSEL: ICC selection

●

OSC1: main clock input for external source (not required on devices without

OSC1/OSC2 pins)

●

VDD: application board power supply (optional, see Note 3)

Note:

If the ICCCLK or ICCDATA pins are only used as outputs in the application, no signal

isolation is necessary. As soon as the Programming Tool is plugged to the board, even if an

ICC session is not in progress, the ICCCLK and ICCDATA pins are not available for the

application. If they are used as inputs by the application, isolation such as a serial resistor

has to be implemented in case another device forces the signal. Refer to the Programming

Tool documentation for recommended resistor values.

During the ICP session, the programming tool must control the RESET pin. This can lead to

conflicts between the programming tool and the application reset circuit if it drives more than

5 mA at high level (push pull output or pull-up resistor<1,000). A schottky diode can be used

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