During operation, the JTAG DTM logic can also be reset without
jtag_reset
by issuing 5
jtag_TCK
clock ticks with
jtag_TMS
asserted. This action resets only the JTAG DTM, not the
debug module.
The JTAG logic always operates in its own clock domain clocked by
jtag_TCK
. The JTAG logic
is fully static and has no minimum clock frequency. The maximum
jtag_TCK
frequency is part-
specific.
The JTAG DTM implements the BYPASS and IDCODE instructions.
On the FE310-G003, the IDCODE is set to
0x20000913
.
The JTAG DEBUG instruction gives access to the SiFive debug module by connecting the
debug scan register between
jtag_TDI
and
jtag_TDO
.
The debug scan register includes a 2-bit opcode field, a 7-bit debug module address field, and a
32-bit data field to allow various memory-mapped read/write operations to be specified with a
single scan of the debug scan register.
These are described in
The RISC‑V Debug Specification 0.13
.
Chapter 21 Debug
FE310-G003 Manual
© SiFive, Inc.
Page 118
Содержание FE310-G003
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