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SPI 16B address and 8b data

 
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beaker404



Joined: 24 Jul 2012
Posts: 163

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SPI 16B address and 8b data
PostPosted: Mon Aug 15, 2022 12:20 pm     Reply with quote

CCS 5.064
PIC18F26K22
EEPROM 93LC66C

Looked around the forum and nothing came out as an exact solution to my problem,
problem being, using a 93LC66 in 8b data mode so 512 x 8 bytes.
Communication is via SPI and works find IF I stay below an address of 255
and I know why, the SPI is only sending 8b of address, tried sending MSB and LSB of the address word, did not work.
Is there a way to get a 16b address to the EEPROM followed by the 8b data? Perhaps I just do not get SPI well enough to resolve it.

SPI set up like this: for 8b data, this all works just not when I try to do 16b addressing.
Code:

#DEFINE SPI_XFER_9356(x)   spi_xfer(SPI2_EEPROM, x)

#DEFINE  EEPROM_ADDRESS unsigned long

#use spi(master, DO=Pin_B3, CLK=PIN_B1, DI=PIN_B2 ,ENABLE_ACTIVE=1, ENABLE_DELAY=20,mode=0, baud=2000000, stream=SPI2_EEPROM, bits=8, FORCE_SW)


my write function:
Code:
void write_ext_eeprom(EEPROM_ADDRESS address, BYTE data)
{

  disable_interrupts(global);           

   output_high(EEPROM_SELECT);
   
   SPI_XFER_9356(0xa);
   
   SPI_XFER_9356(address);
 
   
   SPI_XFER_9356(data);
   
   
   output_low(EEPROM_SELECT);
   
   delay_ms(11);
   enable_interrupts(global);
}


my read function:
Code:
BYTE read_ext_eeprom(EEPROM_ADDRESS address)
{
   BYTE data;
   
   disable_interrupts(global);           
   
   output_high(EEPROM_SELECT);
   
   SPI_XFER_9356(0xc);
   
   SPI_XFER_9356(address);
   
   data=SPI_XFER_9356(0);
   
   
   output_low(EEPROM_SELECT);

   enable_interrupts(global);           
   return(data);

}
beaker404



Joined: 24 Jul 2012
Posts: 163

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PostPosted: Mon Aug 15, 2022 12:22 pm     Reply with quote

sorry for the poor formatting of the thread, for some reason I cannot edit it now correctly.
gaugeguy



Joined: 05 Apr 2011
Posts: 216

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PostPosted: Mon Aug 15, 2022 12:43 pm     Reply with quote

To access addresses 256-511, the high address bit is the low bit of the command.

Code:

output_high(EEPROM_SELECT);

SPI_XFER_9356(0x0c | 0x01);  // command and high bit of address

SPI_XFER_9356(address);  // low 8 bits of address

data=SPI_XFER_9356(0);


output_low(EEPROM_SELECT);
beaker404



Joined: 24 Jul 2012
Posts: 163

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PostPosted: Mon Aug 15, 2022 1:14 pm     Reply with quote

thanks.
Not sure how I missed that in the datasheet,
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