Machine-mode software interrupts are generated by writing to the memory-mapped control reg-
ister
msip
. Each
msip
register is a 32-bit wide
WARL
register where the upper 31 bits are tied to
0. The least significant bit is reflected in the
MSIP
bit of the
mip
CSR. Other bits in the
msip
reg-
ister are hardwired to zero. On reset, each
msip
register is cleared to zero.
Software interrupts are most useful for interprocessor communication in multi-hart systems, as
harts may write each other’s
msip
bits to effect interprocessor interrupts.
mtime
is a 64-bit read-write register that contains the number of cycles counted from the
rtcclk
input described in Chapter 12. A timer interrupt is pending whenever
mtime
is greater than or
equal to the value in the
mtimecmp
register. The timer interrupt is reflected in the
mtip
bit of the
mip
register described in Chapter 8.
On reset,
mtime
is cleared to zero. The
mtimecmp
registers are not reset.
Chapter 9 Core-Local Interruptor (CLINT)
FE310-G003 Manual
© SiFive, Inc.
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