Debug Unit
in the state diagram in figure below. The TAP uses both clock edges of
TCK
.
TMS
and
TDI
are sampled
on the rising edge of
TCK
, while
TDO
changes on the falling edge of
TCK
.
Figure 9.1 TAP Controller State Diagram
Test-Logic-Reset
Run-Test/Idle
Select_DR_Scan
Capture_DR
Shift_DR
Exist1_DR
Pause_DR
Exist2_DR
Update_DR
1
0
0
1
1
0
0
0
1
0
0
0
1
1
0
Select_IR_Scan
Capture_IR
Shift_IR
Exist1_IR
Pause_IR
Exist2_IR
Update_IR
1
1
0
0
0
1
0
0
0
1
1
0
1
1
0
1
0
At power-up the TAP is forced into the
Test-Logic-Reset
by low value on
TRST_N
. The TAP instruction
register is thereby reset to IDCODE. No other parts of the EJTAG hardware are reset through the
Test-Logic-Reset
state.
When test access is required, a protocol is applied via the
TMS
and
TCK
inputs, causing the TAP to exit
the
Test-Logic-Reset
state and move through the appropriate states. From the
Run-Test/Idle
state, an
Instruction register scan or a data register scan can be issued to transition the TAP through the
appropriate states shown in figure below.
The states of the data and instruction register scan blocks are mirror images of each other adding
symmetry to the protocol sequences. The first action that occurs when either block is entered is a
capture operation. For the data registers, the
Capture-DR
state is used to capture (or parallel load) the
data into the selected serial data path. In the Instruction register, the
Capture-IR
state is used to
capture status information into the Instruction register.
From the
Capture
states, the TAP transitions to either the
Shift
or
Exit1
states. Normally the
Shift
state
follows the
Capture
state so that test data or status information can be shifted out for inspection and
new data shifted in. Following the
Shift
state, the TAP either returns to the
Run-Test/Idle
state via the
Exit1
and
Update
states or enters the
Pause
state via
Exit1
. The reason for entering the
Pause
state is
to temporarily suspend the shifting of data through either the Data or Instruction Register while a
XBurst®2
CPU Core Programming Manual
Copyright © 2005-2020 Ingenic Semiconductor Co., Ltd. All rights reserved.
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