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ISD17240 voice recorder chip timing problem

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cincailo

New Member
Hello everyone! I'm using a PIC to control for the recording and playback of the voice recorder chip, ISD17240. But then facing a problem to synchronize both the chip. Since I'm using the SPI method where PIC is master while ISD17240 is slave so every MISO and MOSI need clock to send or receive data. My PIC has a crystal which generate clock pulse but it is much higher than the ISD17240 needed. Any suggestion in making the two chips have the same clock? Or actually it is not the crystal to give the clock pulse to both PIC and ISD17240 clock pin for receiving and transmitting data?

Thanks.
 

duffy

Well-Known Member
It's not the crystal, there is a separate SPI clock pin (SCK) on the Pic chip for synchronous serial communications. Check un the USART section of the spec sheet, there are actually 4 pins for the SPI - SDI, SDO, SCK, and /SS.
 

cincailo

New Member
Yes, I know there are 4 pins for SPI. So want to know that SCK = Fosc/4 ? The Fosc is crystal? Is it I just need to change the SCK to a value that suit the slave?
 

duffy

Well-Known Member
One of the SSPCON registers allows you to select the frequency for the SPI port clock signal. You can typically divide Fosc by 4, 16, and 64. If that is still too fast, you have the option to use one of the timers as the frequency generator for SCK.

The spec sheet is your friend, read the spec sheet.
 
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