Table 104:
Test and Debug Data Register 3
Breakpoint Control Register (
mcontrol
)
27
dmode
RW
0
Debug-Only access mode
[31:28]
type
RO
2
Address/Data match type, always 2
The
type
field is a 4-bit read-only field holding the value 2 to indicate this is a breakpoint con-
taining address match logic.
The
bpaction
field is an 8-bit read-write
WARL
field that specifies the available actions when
the address match is successful. The value 0 generates a breakpoint exception. The value 1
enters debug mode. Other actions are not implemented.
The R/W/X bits are individual
WARL
fields, and if set, indicate an address match should only be
successful for loads/stores/instruction fetches, respectively, and all combinations of imple-
mented bits must be supported.
The M/S/U bits are individual
WARL
fields, and if set, indicate that an address match should
only be successful in the machine/supervisor/user modes, respectively, and all combinations of
implemented bits must be supported.
The
match
field is a 4-bit read-write
WARL
field that encodes the type of address range for
breakpoint address matching. Three different
match
settings are currently supported: exact,
NAPOT, and arbitrary range. A single breakpoint register supports both exact address matches
and matches with address ranges that are naturally aligned powers-of-two (NAPOT) in size.
Breakpoint registers can be paired to specify arbitrary exact ranges, with the lower-numbered
breakpoint register giving the byte address at the bottom of the range and the higher-numbered
breakpoint register giving the address 1 byte above the breakpoint range, and using the
chain
bit to indicate both must match for the action to be taken.
NAPOT ranges make use of low-order bits of the associated breakpoint address register to
encode the size of the range as follows:
Table 105:
NAPOT Size Encoding
maddress
Match type and size
a…aaaaaa
Exact 1 byte
a…aaaaa0
2-byte NAPOT range
a…aaaa01
4-byte NAPOT range
a…aaa011
8-byte NAPOT range
a…aa0111
16-byte NAPOT range
Chapter 21 Debug
FE310-G003 Manual
© SiFive, Inc.
Page 114
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