Tapc State Machine - STMicroelectronics SPC572L series Reference Manual

IEEE 1149.7 Compact JTAG Test Access Port Controller (CJTAG)
60.5.4.3.1 Custom escape sequence
An online technology can use the custom escape sequence in any manner it chooses. It is
used as the End of Transmission (EOT) of certain data types (formats OScan4-7) with T4
and above TAP.7s.
60.5.4.3.2 Reset escape sequences
A reset event initializes all technologies sharing the TCK(C) and TMS(C) connectivity. A
reset escape sequence resets the technology. It is recommended that this reset occur with
the falling edge of TCKC. With a TAP.7 controller a reset escape sequence generates a
Type-3 reset beginning with the falling edge of TCK(C) following the asynchronous detection
of the event.
60.5.5

TAPC State Machine

T1 and above TAP.7s require knowledge of the TAPC state machine state. With T2 and
above TAPs this knowledge must be developed independently of the CLTAPC. This is
generally accomplished by implementing a TAPC state machine within the EPU. This TAPC
state machine provides the function of the state machine within a standard 1149.1 TAPC. It
is recommended that this state machine is implemented to change state on the falling edge
of TCK(C) as this has numerous advantages to a TAP.7 controller. The EPU does not
contain 1149.1 Instruction or Data Registers. The APU controls the state changes of this
TAPC state machine with T4 and above TAP.7s.
1756/2058 DocID027809 Rev 4
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