Stm32F446Xx Jtag Tap Connection; Figure 444. Jtag Tap Connections - ST STM32F446 Series Reference Manual

RM0390
33.5

STM32F446xx JTAG TAP connection

The STM32F446xx MCUs integrate two serially connected JTAG TAPs, the boundary scan
TAP (IR is 5-bit wide) and the Cortex
To access the TAP of the Cortex
1. First, it is necessary to shift the BYPASS instruction of the boundary scan TAP.
2. Then, for each IR shift, the scan chain contains 9 bits (=5+4) and the unused TAP
instruction must be shifted in using the BYPASS instruction.
3. For each data shift, the unused TAP, which is in BYPASS mode, adds 1 extra data bit in
the data scan chain.
Note: Important: Once Serial-Wire is selected using the dedicated Arm
boundary scan TAP is automatically disabled (JTMS forced high).
®
-M4 with FPU TAP (IR is 4-bit wide).
®
-M4 with FPU for debug purposes:

Figure 444. JTAG TAP connections

RM0390 Rev 4
Debug support (DBG)
®
JTAG sequence, the
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