AN1474
APPLICATION NOTE
ST92F150 AND ST92F120 PROBLEM RESOLUTION
GUIDELINES
by Microcontroller Division Applications
INTRODUCTION
The ST92F120 and ST92F150 are part of the same family of powerful microcontrollers from
STMicroelectronics, featuring single voltage flash memory and an innovative E3prom concept.
This document gives guidelines on resolving several common application problems that have
been reported by ST Application Engineers.
Testflash features
The testflash features are described in the ST92F120 and ST92F150 datasheets.
Located in a reserved flash area, the TestFlash contains the bootcode which performs the
E3prom initialization, provides the possibility to program the flash by In System Programming
(refer to the application note
AN1450 ST9 Flash Programming
for a detailed description) and
then jumps to the start address application code via the reset vector.
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ST92F150 AND ST92F120 PROBLEM RESOLUTION GUIDELINES
1 EXTERNAL WATCHDOG ROUTINE
During the bootcode execution (from 12.5 ms up to 75ms if an aborted E3prom write operation
is detected), a code routine provided by the user may be executed to refresh an external
watchdog.
The routine address offset is located at addresses 0x000006h and 0x000007h while the seg-
ment where the routine is located has to be written in 0x000009h.
You must fill the word at the address 0x000006h with 0xffffh if your application does not use an
external watchdog.
Startup file example (usually called crtbegin.spp) :
.org 0x06
.word 0xffff
Refer to the application examples provided with the ST9+ User Guide.
1.1 PROBLEM DESCRIPTION
The application is not executed at all and it is not possible to communicate by ISP with the pro-
gramming board.
1.2 ANALYSIS
When the chip is read directly with the programming board, the contents of addresses
0x000006h and 0x000007h is not equal to 0xFFh.
These addresses in the application code are not equal to 0xFF whereas an external watchdog
routine is not provided.
1.3 RESOLUTION
Modify the application code as mentioned at the beginning of this section and erase and re-
program the device.
There is no way to modify this chip by ISP, it has to be unsoldered.
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ST92F150 AND ST92F120 PROBLEM RESOLUTION GUIDELINES
2 ST92F120 RESET VECTOR
One of the powerful features provided by the ST9 Flash device family is the possibility to up-
grade the application code by downloading and programming through an I/O interface on the
MCU (refer to the application note
AN1275 In Application Programming for the ST92F120
for
a detailled description).
In case of a parasitic reset during the flash upgrade operation, the application must be able to
recover safely by executing the bootloader code.
To perform this, the bootloader is present in the flash sector where the application starts, the
one pointed to by the reset vector. This sector must never be erased.
This is why the reset vector is always located in the smallest sector.
ST92F120 60Kbyte Flash device map
Sector
F0
F1
F2
Size
4 Kbyte
48 Kbyte
8 Kbyte
ST92F120 128Kbyte Flash device map
Sector
F0
F1
F2
F3
Size
64 Kbyte
48 Kbyte
8 Kbyte
8 Kbyte
ST92F150 60 Kbyte Flash device map
Sector
F0
F1
F2
F3
Size
8 Kbyte
8 Kbyte
32 Kbyte
12 Kbyte
ST92F150 128Kbyte Flash device map
Sector
F0
F1
F2
F3
Size
8 Kbyte
8 Kbyte
48 Kbyte
64 Kbyte
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ST92F150 AND ST92F120 PROBLEM RESOLUTION GUIDELINES
2.1 SPECIAL RESET VECTOR MAPPING IN ST92F120 128KBYTE FLASH DEVICE
The reset vector is located at the beginning of Sector F0, at address 0x000000, in all
ST92F150 and ST92F120 microcontrollers but one : the ST92F120 128Kbyte Flash device. In
this device, the reset vector is located in 0x01E000h, at the begining of the sector F3.
The ST92F120 emulator has the same behaviour as the ST92F120 60Kbyte Flash device : its
reset vector is located in 0x000000h, at the beginning of Sector F0.
So, how to emulate an ST92F120 128Kbyte Flash device ?
There are two possibilities :
1. The application startup code is located in Sector F3 and an instruction is added to jump
from Sector F0 to Sector F3. This jump is executed by the emulator but not by the final
application.
2. The application startup code is located in F3 and an instruction is added to jump from Sec-
tor F3 to Sector F0. This jump is executed by the final application but not by the emulator.
2.1.1 Jump from Sector F0 to F3
If the application starts in Sector F3 (for example if you are developing an IAP bootloader), a
line of code has to be added in Sector F0 to jump to the reset vector. This way the emulator will
jump to the beginning of the application, executing just one more instruction than the chip.
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ST92F150 AND ST92F120 PROBLEM RESOLUTION GUIDELINES
Example, resetf0.spp :
;Use this file only when emulating the code
#include "config.spp"
#include "define.h"
PROGRAMMING_MODEL
.section .init
;emulator reset vector redirection
.word __ResetF0
.org
.word
.org
0x06
0xffff
0x0a
;external watchdog routine vector
.proc __ResetF0
__ResetF0:
jps seg(__Reset), sof(__Reset)
.endproc __ResetF0
This file must be defined in the makefile.mak as a spp source file.
Example :
# Give here the name of the C/SPP/ASM source files used in the appli-
cation
C_SRC = main.c
SPP_SRC =
resetf0.spp
ASM_SRC =
# Give here the name of the stratup files used in the application
STARTUP_SRC = crtbegin.spp crtend.spp
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