PM0020 datasheet(40/87 Pages) STMICROELECTRONICS

40 / 87 page

STR91xFA Flash memory

PM00020

40/87

1.16

STR91x in-application programming (IAP)

An important requirement for most Flash-based systems is the ability to update firmware

while the system is installed in the end product. This is referred to as In-Application

Programming (IAP).

STR91x MCUs have the capability of running user-specific firmware to perform In

Application Programming of the MCU embedded Flash memory. This feature allows the use

of any type of communication protocol for the reprogramming process (for example, CAN,

UART, USB etc …).

The principle is to program the user application in Bank0 using code located in Bank1.

The diagram below outlines general STR91x IAP guidelines.

Figure 2.

IAP general flowchart

Bank1 is remapped in hardware to address 0x00 and Bank0 is remapped in hardware to 0x80000 (if Bank0

size is 256 or 512 Kbytes) and to 0x200000 (if Bank0 size is 1 or 2 Mbytes). The base address must be at

a 32 Kbyte boundary for Bank1. For Bank0, it must be at a 512 Kbyte boundary or at a 2 Mbyte boundary.

The condition can be, for example, a pin level allowing either to execute the IAP driver located in Bank1 or

to jump to the user application located in Bank0 after being loaded using IAP.

If the user application doesn't contain interrupts, there is no problem. A problem is encountered when the

user application (remapped to the new address) contains interrupts because the interrupt vector is located

at address 0x00. Consequently, interrupts must be redirected to Bank0.

False

True

Remap Bank1 and Bank0 in hardware

using the CAPS tool1)

Load the IAP driver in Bank 1

using a toolset

Condition2)

Execute the IAP driver

to reprogram Bank0

Jump to new Bank0 base

address to execute the

application program3)

Application program

PM0020 Datasheet(PDF) 40 Page - STMicroelectronics