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If CAFRZ=1, the cache is frozen (the cache
content is locked).
To change CAFRZ bit use: IEE, Slide 95 BCLR CAFRZ ; Clear CAFRZ
BSET CAFRZ ; Set CAFRZ Copyrigh CBERR Bit of ST3_55 IEE, Slide 96 CBERR is the « CPU bus error flag »
The CBERR bit is set when an internal bus error is
detected. An error causes the CPU to set the bus error
interrupt flag (BERRINTF) in IFR1.
The interrupt service routine for the bus error
interrupt (BERRINT) must clear the CBERR bit
before it returns control to the interrupted program
using: BCLR CBERR ; Clear CBERR
If CBERR =0 The flag has been cleared by program
or by a reset.
CBERR=1 An internal bus error has been detected. Copyrigh CLKOFF Bit of ST3_55 CLKOFF bit disables CLKOUT
If CLKOFF = 1, the output of the
CLKOUT pin is disabled and remains
at a high level.
Set and clear by:
BCLR CLKOFF ; Clear CLKOFF BSET CLKOFF ; Set CLKOFF IEE, Slide 97 Copyrigh HINT Bit of ST3_55 IEE, Slide 98 HINT: Host interrupt bit is used to send
an interrupt request to a host processor
by the way of the host port interface.
To produce an active-low interrupt
pulse clear and then set the HINT bit:
BCLR HINT ; Clear HINT
BSET HINT ; Set HINT Copyrigh MPNMC Bit of ST3_55
MPNMC • MPNMC defines the Microprocessor / MicroMPNMC
computer • MPNMC reflects the logic level on the MP/MC
pin when the pin is sampled at reset
pin • The MPNMC bit enables or disables the on-chip
ROM. If MPNMC=0 Microcomputer mode. The on-chip ROM is enabled; it is addressable in program space.
ROM If MPNMC=1 Microprocessor mode. The on-chip
ROM is disabled; it is not in the program-space map.
ROM IEE, Slide 99 Copyrigh SATA Bit of ST3_55 SATA is the Saturation mode bit for the A
SATA bit determines whether the CPU
saturates overflow results of the A-unit
arithmetic logic unit (A-unit ALU):
arithmetic If SATA=0 No saturation is performed. If SATA=1 On. If result is in overflow,
result is saturated to 7FFFh or 8000h (for
positive or negative overflow respectively).
Can be cleared and set by: IEE, Slide 100 BCLR SATA ; Clear SATA
BSET SATA ; Set SATA Copyrigh SMUL Bit of ST3_55 SMUL is the Saturation-on-multiplication
If SMUL =0 Off
If SMUL =1 On.
SMUL=1 forces the product of the two
negative numbers to be a positive number.
instructions, the saturation is performed after
the multiplication and before the
Clear and set SMUL with : IEE, Slide 101 BCLR SMUL ; Clear SMUL
BSET SMUL ; Set SMUL Copyrigh SST Bit of ST3_55 IEE, Slide 102 SST is the Saturate-on-store mode bit used
in the C54-compatible mode (C54CM=1)
If C54CM=0 SST is ignored by the C55x.
If C54CM = 1: SST turns the saturationon-store mode on or off.
SST= 0 no saturation
SST=1 CPU saturates a shifted or
unshifted accumulator value before
storing it. The saturation depends on the
value of the sign-extension mode bit
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- Spring '14