AN977 Datasheet, PDF (9/17 Pages) STMicroelectronics – GUIDELINES FOR UPGRADING FROM THE ST92F120

GUIDELINES FOR UPGRADING FROM THE ST92F120 (0.50 µm) TO THE ST92F124...
1.10.1 START EVENT REQUEST
A difference between the ST92F120 and the ST92F124/F150/F250 I²C exists on the START
bit generation mechanism.
To generate a START event, the application code sets the START and ACK bits in the I2CCR
register:
– I2CCCR |= I2Cm_START + I2Cm_ACK;
Without the compiler optimization option selected, it is translated in assembler the following
way:
– or R240,#12
– ld r0,R240
– ld R240,r0
The OR instruction sets the Start bit. On the ST92F124/F150/F250, the second load instruc-
tion execution results in a second START event request. This second START event occurs
after the next byte transmission.
With any of the compiler optimization options selected, the assembler code does not request
a second START event:
– or R240,#12
1.11 NEW PERIPHERALS
– Up to 2 CAN (Controller Area Network) cells have been added. Specifications are available
in the updated ST92F124/F150/F250 Datasheet.
– Up to 2 SCIs are available: the SCI-M (Multi-protocol SCI) is the same as on the ST92F120,
but the SCI-A (Asynchronous SCI) is new. The specifications for this new peripheral are
available in the updated ST92F124/F150/F250 Datasheet.
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