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ON-BOARD PROGRAMMING METHODS FOR XFLASH AND HDFLASH ST7 MCUs

1 APPLICATION NOT RUNNING DURING PROGRAMMING

This case covers applications that can be stopped during the programming operation: either

because there is no need to keep the application running, or because the programming

process does not require any special firmware to be run by the MCU. This last point means the

application design is compatible with the programming method and tools used.

For this purpose, STMicroelectronics has defined an In Circuit Programming (ICP) method

with a minimum of constraints on the application design.

1.1 ICP OVERVIEW

With this method, the MCU is switched by the programming tool into a special operating mode,

called In Circuit Communication (ICC) mode, by an event sequence on the RESET, VPP/

TEST, ICCCLK and ICCDATA pins: Throughout the entire programming operation, it remains

under control of the programming tool and all transactions go through the ICCCLK and

ICCDATA lines.

In order to be compatible with the ICP method, the application must therefore be equipped

with a special connector for the RESET, VPP/TEST, ICCCLK and ICCDATA signals, while re-

specting some guidelines in order not to interfere with other parts of the application.

Note that this connector features a VPP/TEST line to allow to supply 12V externally on the

VPP pin for HDFLASH-based devices.

When using the ICP method, the user has exactly the same features as on any programming

tool: the whole program memory range, as well as the option bytes can be accessed.

1.2 ICP PRACTICAL IMPLEMENTATION

The ICP implementation is purely a hardware issue as shown in Figure 1. No embedded

firmware needs to be developed. On the other words, the ICP method can be used to program

a blank MCU.

The only sensitive point is sometimes to correctly isolate the RESET, ICCCLK and ICCDATA

in order to avoid any conflict with the devices connected to these pins for purposes of the final

application. This is generally ensured by simple resistors (more details can be found in the

MCU datasheets or in the ST7 ICC Reference Manual).

During the ICP process, the MCU’s embedded peripherals remain in reset state since no soft-

ware is running to activate them. It should be noted however that the hardware watchdog is

disabled.

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