CP_SetDiv*

Syntax

#include <nitro/cp.h>

void CP_SetDiv32_32( u32 numer, u32 denom );
void CP_SetDiv64_32( u64 numer, u32 denom );
void CP_SetDiv64_64( u64 numer, u64 denom );

Arguments

numer Numerator of fraction. Represents dividend of division here.
denom Denominator of fraction. Represents divisor of division here.

Return Values

None.

Description

Sets parameters for division. Sets division mode first, and then stores dividend and divisor in each register. CP_SetDivImm* is used to store dividend and divisor.

There are three division modes as follows:

Division Mode Calculation Results Calculation Cycles CPU Cycle Conversion
CP_DIV_32_32BIT_MODE 32-bit divided by 32-bit Quotient 32-bit, remainder 32-bit 18 cycles 36 cycles
CP_DIV_64_32BIT_MODE 64-bit divided by 32-bit Quotient 64-bit, remainder 32-bit 34 cycles 68 cycles
CP_DIV_64_64BIT_MODE 64-bit divided by 64-bit Quotient 64-bit, remainder 64-bit 34 cycles 68 cycles


Set mode to CP_DIV_32_32BIT_MODE with CP_SetDiv32_32().

Set mode to CP_DIV_64_32BIT_MODE with CP_SetDiv64_32().

Set mode to CP_DIV_64_64BIT_MODE with CP_SetDiv64_64().

Caution: With the divider, sometimes the value is overwritten in the interrupt. If the division parameters are set up and an interrupt occurs during division when a divider is used, the original calculated result will be broken. Therefore, if you are using the divider in an interrupt, the status of the divider needs to be temporarily stored and restored using CP_SaveContext() and CP_RestoreContext(), respectively. Status of the divider is also automatically saved/restored when threads are switched.


Example: Restore the status of the divider.

intr_func( void ) 
{
  CPContext context;
       
  CP_SaveContext( &context );
  CP_SetDiv32_32( 1000, 5 );
  CP_WaitDiv();
  result = CP_GetDivResult();
  CP_RestoreContext( &context );
}

Internal Operation

Stores values in DIVCNT(0x4000280), DIV_NUMER(0x4000290), and DIV_DENOM(0x4000298) of the IO register.

See Also

CP_SetDivImm*, CP_IsDivBusy, CP_WaitDiv, CP_GetDivResult*, CP_GetDivRemainder*, CP_SaveContext, CP_RestoreContext

Revision History

2006/08/09 Added a description of the number of calculation cycles.
2005/03/08 Standardized the Japanese term for "interrupt."
2004/11/02 Corrected IO register address in Internal Operation.
2004/05/06 Changes to description as a result of making process thread-safe.
2004/03/31 Indicated that process is not thread-safe.
2004/01/09 Added content.
2003/12/01 Initial version.


CONFIDENTIAL