Digital

NAME

fpc − floating-point control registers

SYNOPSIS

#include <machine/fpu.h>

int get_fpc_csr()

int set_fpc_csr(csr)
int csr;

int get_fpc_irr()

int get_fpc_eir()

void set_fpc_led(value)
int value;

int swapRM(x)
int x;

int swapINX(x)
int x;

DESCRIPTION

These routines are to get and set the floating-point control registers of MIPS floating-point units. All of these routines take and or return their values as 32 bit integers. 

The file <machine/fpu.h> contains unions for each of the control registers. Each union contains a structure that breaks out the bit fields into the logical parts for each control register. This file also contains constants for fields of the control registers.

All implementations of MIPS floating-point have a control and status register and a implementation revsion register.  The control and status register is returned by get_fpc_csr. The routine set_fpc_csr sets the control and status register and returns the old value.  The implementation revsion register is read-only and is returned by the routine get_fpc_irr.

The R2360 floating-point units (floating-point boards) have two addtitonal control registers. The exception instruction register is a read-only register and is returned by the routine get_fpc_eir. The other floating-point control register on the R2360 is the leds register. The low 8 bits corresponds to the leds where a one is off and a zero is on. The leds register is a write-only register and is set with the routine set_fpc_leds.

The routine swapRN sets only the rounding mode and returns the old rounding mode.  The routine swapINX sets only the sticky inexact bit and returns the old one.  The bits in the arguments and return values to swapRN and swapINX are right justified. 

ALSO SEE

R2010 Floating Point Coprocessor Architecture
R2360 Floating Point Board Product Description