AN977 Datasheet, PDF (10/17 Pages) STMicroelectronics – GUIDELINES FOR UPGRADING FROM THE ST92F120

GUIDELINES FOR UPGRADING FROM THE ST92F120 (0.50 µm) TO THE ST92F124...
2 HARDWARE & SOFTWARE MODIFICATIONS TO THE APPLICATION BOARD
2.1 PINOUT
– Due to its remapping, CLOCK2 can not be used in the same application.
– SCI1 can only be used in asynchronous mode (SCI-A).
– The modifications of the analog input channels mapping can be easily handled by software.
2.2 INTERNAL VOLTAGE REGULATOR
Due to the presence of the internal voltage regulator, external capacitors are required on the
Vreg pins in order to provide the core with a stabilized power supply. In the ST92F124/F150/
F250, the core operates at 3.3V, while the I/Os still operate at 5V. The minimum recom-
mended value is 600 nF or 2*300 nF and the distance between the Vreg pins and the capac-
itors must be kept to a minimum.
No other modifications need to be made to the hardware application board.
2.3 FLASH & EEPROM CONTROL REGISTERS AND MEMORY ORGANIZATION
To save 1 DPR, the symbol address definitions that correspond to the Flash and EEPROM
control registers can be modified. This is generally done in the linker script file. The 4 registers,
FCR, ECR, and FESR[0:1], have been defined at 0x221000, 0x221001, 0x221002 and
0x221003, respectively.
The 128-Kbyte Flash sector reorganization also affects the linker script file. It must be modi-
fied in compliance with the new sector organization.
Refer to Section 1.4.2 for the description of the new Flash sector organization.
2.4 RESET AND CLOCK CONTROL UNIT
2.4.1 Oscillator
2.4.1.1 Crystal Oscillator
Even if the compatibility with the ST92F120 board design is maintained, it is no longer recom-
mended to insert a 1MOhm resistor in parallel with the external crystal oscillator on a
ST92F124/F150/F250 application board.
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