AN2078

IAP overview

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1

IAP overview

1.1

Principle

The IAP driver must be programmed by the user in the Flash base address (0x00) via JTAG

using a flasher toolset.

Using the UART, the IAP driver loads a binary file from the HyperTerminal to the STR7xx

internal Flash, and then jumps to execute it.

1.2

IAP driver description

The following table shows the IAP driver code size for each STR7xx MCU.

The IAP driver contains a set of source files:

●

main.c: where the UART initialization and PLL configuration are set. Then, a main

menu is executed from the common.c file.

●

common.c: contains display functions and the main menu routine. The main menu

gives the choice between loading a new binary file and executing the binary file already

loaded.

●

ymodem.c and download.c: they allow all data to be received from the HyperTerminal

the event of a failure in data receival, the ‘Failed to receive the file’ error message is

displayed on the HyperTerminal window. However, if successful, the data is then

programmed into internal Flash at the appropriate address. A comparison between

internal RAM and internal Flash contents is performed to check the data intergrity. If

there is any discrepency, the ‘Verification failed’ error message is displayed on

HyperTerminal window. Other error messages are also displayed when the image size

is higher than the allowed space memory and when there is an abort by the user.

Note:

1

Ymodem protocol sends data in 1024-byte blocks. A check for errors in data blocks

transmitted to the STR7xx Internal RAM is applied: A comparison between the transmitted

and received data is achieved. Blocks received unsuccessfully are acknowledged with a

NAK (Negative Acknowledgement). For more details about the Ymodem protocol, refer to

existing documentation.

●

Some STR7xx Standard library and Flash library files.

A pin connected to a push button is used to select between jumping to the user application

and executing the IAP for reprogramming purpose:

●

Push button is not pressed at reset: jump to the user application

●

Push button is pressed at reset: the IAP main menu is displayed

Figure 1 shows the IAP flowchart.

STR71x

STR73x

STR75x

7.2 Kbytes

8.3 Kbytes

5.8 Kbytes