Cirrus Logic AN74 - Manual (Page 9)

AN74
AN74Rev2 9
/**************************************************************************************
* Routine - read_register
* Input
- command
* Output - low_byte, mid_byte, high_byte
*
* This subroutine reads an internal register of the ADC
/**************************************************************************************/
void
read_register(char command){
if(mode == 1) P1 = 0xF4;
/*Assert CS if necessary */
transfer_byte(command); /*Transfer Command Byte to CS5525/6/9*/
high_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/
mid_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/
low_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/
if(mode == 1)P1 = 0xF5; /*Deassert CS if necessary */
}
/**************************************************************************************/
* Routine - acquire_conversion
* Input
- command
* Output - Conversion results in memory locations HIGHBYTE, MIDBYTE and
*
LOWBYTE. This algorithm performs only single conversions. If
* continuous conversions are needed the routine needs to be
* modified. Port flag is zero.
*
*
HIGHBYTE MIDBYTE LOWBYTE
* 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
* 16-bit results MSB LSB 1 1 1 1 0 0 OD OF
* 20-bit results MSB LSB 0 0 OD OF
* This subroutine initiates a single conversion.
/**************************************************************************************/
void
acquire_conversion(char command){
/*** Read Configuration Register to Prevent Previously Set Bits from being Altered ***/
read_register(0x94);
/*Read Configuration Register*/
low_byte = low_byte|0x20; /*Assert Port Flag Bit*/
write_to_register(0x84,low_byte, mid_byte, high_byte);/*Actually Send Commands*/
/*Acquire a Conversion*/
if(mode == 1)P1
= 0xF4; /*Assert CS if necessary*/
transfer_byte(0xC0); /*Transfer Command to CS5525/6/9*/
toggle_sdo(); /*Clear SDO*/
high_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/
mid_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/
low_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/
if(mode == 1) P1 = 0xF5; /*Deassert CS if necessary*/
}