Epu (Extended Protocol Unit) Operation - STMicroelectronics SPC572L series Reference Manual

RM0400
60.6

EPU (Extended Protocol Unit) Operation

60.6.1 EPU Operation
The EPU adds functionality to the BYPASS and IDCODE instructions.
60.6.1.1 Zero-bit DR-Scans (ZBS)
A zero-bit DR-Scan (ZBS) is a TAPC-state sequence that begins with the Select-DR-Scan
state and ends with an exit from the Update-DR state without an intervening Shift-DR state.
The external tool controls the EPU using ZBSs.
The use of ZBSs can begin immediately following the Test-Logic-Reset state since this state
initializes the Instruction Registers of TAPs with either the BYPASS or IDCODE instructions.
60.6.1.2 Utilizing ZBSs for TAP.7 Controller Functionality
Beginning with a ZBS count of zero, the ZBS count is incremented with each consecutive
occurrence of a ZBS without encountering a Shift-DR state. This count cannot be
IEEE 1149.7 Compact JTAG Test Access Port Controller (CJTAG)
Figure 1032. Falling edge TAP controller state machine
TMS=1
Test-Logic
Reset
TMS=0
TMS=1
Run-Test-Idle
TMS=0
TMS=1
DocID027809 Rev 4
TMS=1
Select-DR
TMS=0
TMS=1
Capture-DR
TMS=0 TMS=0
Shift-DR
TMS=1
Exit1-DR
TMS=0 TMS=0
Pause-DR
TMS=1
TMS=0
Exit2-DR
TMS=1
Update-DR
TMS=1
TMS=0
Select-IR
TMS=1
TMS=0
TMS=1
Capture-IR
TMS=0 TMS=0
Shift-IR
TMS=1
TMS=1
Exit1=IR
TMS=0 TMS=0
Pause-IR
TMS=1
TMS=0
Exit2-IR
TMS=1
Update-IR
TMS=1
TMS=0
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