Two problems with SX-B & SX48

paolo

Hi,
I think I've found two problems with the SXB compiler v. 1.51.03 when used with the SX48 chip.

First problem:

The I2CSTOP function modifies the data direction register of the port associated with the SDA and SCL lines.

Example:

SDA var ra.0
SCL var ra.1

The function I2CSTOP SDA may randomly change the direction of the lines RA.2 and RA.3
This happens because the compiled code loads the tris_a register with the value in __PARAM1.

Suggested workaround:
Initialize __PARAM1 with the value of the tris_a register before calling I2CSTOP
e.g.
__param1 = tris_a
I2CSTOP SDA


Second problem:

The interrupt routine does not preserve the value of __PARAMCNT (which shares the register __PARAM5).
As a result, if, from the interrupt, you call a subroutine with a variable number of parameters, you can get unexpected results from your code.

Suggested workaround:
Use the following code:

INTERRUPT NOCODE
ASM
CLR FSR
MOV __INTPARAMFSR,__PARAM1
MOV __INTPARAMFSR+1,__PARAM2
MOV __INTPARAMFSR+2,__PARAM3
MOV __INTPARAMFSR+3,__PARAM4
MOV __INTPARAMFSR+4,__PARAM5 ;
ENDASM
BANK

....your interrupt code

ASM
CLR FSR
MOV __PARAM1,__INTPARAMFSR
MOV __PARAM2,__INTPARAMFSR+1
MOV __PARAM3,__INTPARAMFSR+2
MOV __PARAM4,__INTPARAMFSR+3
MOV __PARAM5,__INTPARAMFSR+4
ENDASM
RETURNINT

Bean

Paolo,
· Thank you for letting me know about these.
· The __PARAM5 problem has already been fixed, but the I2CSTOP bug is a new find.
· The "MOV FSR,#__PARAM1" should be omitted.
·I will make sure it is fixed in the next release.

Thanks again,

Bean.

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·

paolo

Good, thank you Bean.

Paolo