Figure 385. Jtag Tap State Machine - STMicroelectronics STM32WL5 Series Reference Manual

RM0453
JTMS=1
Test-Logic-
Reset
JTMS=0
JTMS=0
Run-Test/
Idle
The operation of the JTAG-DP is as follows:
•
When the TAPSM goes through the Capture-IR state, 0b0001 is transferred onto the
instruction register (IR) scan chain. The IR scan chain is connected between JTDI and
JTDO.
•
While the TAPSM is in the Shift-IR state, the IR scan chain shifts one bit for each rising
edge of JTCK. This means that, on the first tick:
–
–
–
•
When the TAPSM goes through the Update-IR state, the value scanned into the IR
scan chain is transferred into the instruction register.
•
When the TAPSM goes through the Capture-DR state, a value is transferred from one
of the data registers onto one of the DR scan chains, connected between JTDI and
JTDO.
•
The value held in the instruction register determines which data register and associated
DR scan chain are selected.

Figure 385. JTAG TAP state machine

JTMS=1
JTMS=1
JTMS=0
JTMS=1
JTMS=0
JTMS=1
JTMS=0
JTMS=1
JTMS=1
The LSB of the IR scan chain is output on JTDO.
Bit[n] of the IR scan chain is transferred to bit[n-1].
The value on JTDI is transferred to the MSB of the IR scan chain.
JTMS=1
Select-
DR-Scan
JTMS=0
Capture-
DR
Shift-DR
JTMS=0
JTMS=1
Exit1-DR
Pause-
DR
JTMS=0
Exit2-DR
Update-
DR
JTMS=0
RM0453 Rev 5
Debug support (DBG)
Select-
IR-Scan
JTMS=0
JTMS=1
Capture-
IR
JTMS=0
Shift-IR
JTMS=1 JTMS=0
Exit1-IR
JTMS=0
Pause-IR
JTMS=1
JTMS=0
JTMS=0
Exit2-IR
JTMS=1
Update-
IR
JTMS=1 JTMS=0
JTMS=1
JTMS=1
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