Hi,

Anyone using the CCS PCM built-in SPI drivers in slave mode?

There is no documentation or demonstration code for the slave mode but, on
trying it out, it seems that writing constants as opposed to a variable
generates different code..Code generated for the constant actually reads
the SSPBUF (and discards the data) prior to writing data to it whereas the
variable code ignores this and loses it's way after a while...

0000                01189 ....................                                   spi_write(0x02);
01FF 1283           01190 BCF    03,5
0200 0813           01191 MOVF   13,W
0201 3002           01192 MOVLW  02
0202 0093           01193 MOVWF  13
0203 1683           01194 BSF    03,5
0204 1814           01195 BTFSC  14,0
0205 2A08           01196 GOTO   208
0206 1283           01197 BCF    03,5
0207 2A03           01198 GOTO   203

opposed to :

0000                01269 ....................                                   spi_write(Data);
024E 0821           01270 MOVF   21,W
024F 0093           01271 MOVWF  13
0250 1683           01272 BSF    03,5
0251 1814           01273 BTFSC  14,0
0252 2A55           01274 GOTO   255
0253 1283           01275 BCF    03,5
0254 2A50           01276 GOTO   250

Presumably, this doesnt make a difference as long as, if you need to read data from the SPI for every byte received, then you always do a read first
otherwise the write instruction may have chucked it.
Am I missing a trick, somewhere, or is this a known flakiness?

Regards,
Dan

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