Public Version
ICEPick Module
www.ti.com
Bits
Field Name
Description
Type
Reset
18
SPONTDISCOFLAG
This flag is set if the TAPs are spontaneously removed from the
RW
0 (POR)
scan chain or if a selected TAP looses power. It also forces the TDO
output to HiZ.
Writing a 1 to this bit clears it. Writing a 0 has no effect.
17:16
DESELECTMODE
See
RW
0 (POR)
15:6
KEYSEQUENCE
When the TAPLinkMode is set to "key sequence", this field contains
RW
0 (POR)
the "key sequence pattern" that will make the ICEPick TAP visible
again. 0x2CD is the recommended value. Another 10-bit sequence
may be used. During KeySequence detection, LSB of the Key
sequence should be shifted into TDI first.
5:4
ESERVED
Reserved, Read return reset value, write reset value for further
R
0
compatibility
3:1
TAPLINKMODE
See
RW
0 (POR)
0
ActivateMode
When a 1 is written to this bit, the currently selected TAPLinkMode is
RW
0 (POR)
activated. ICEPick will link the TAPs according to these settings
when the ICEPick TAP is advanced to Run-Test/Idle with any
opcode in the IR.
When in key-sequence mode, this bit is automatically cleared when
the key sequence is detected.
NOTE:
These registers are updated when entering the Update DR state, but the action that results
from the update occurs when entering the Run Test/Idle state.
Table 27-20. DESELECTMODE Values
Value
Mode
Behavior
00
Stay-selected
Even though a selected secondary TAP becomes inaccessible, the set of selected TAPs
does not change. Scan to any and all modules may not be possible.
01
Reserved
Acts like Stay-Selected
10
Reserved
Acts like Stay-Selected
11
Auto-deselect
When a selected secondary TAP becomes inaccessible due to power constraints, all
secondary TAPs are deselected. TDO is forced to Hiz.
Table 27-21. TAPLINKMODE Values
Value
Mode
Behavior
000
Always-first
The ICEPick TAP always exists and is linked as the TAP closest to TDI.
001
Reserved
Reserved (behaves like Always-first)
010
Key-Sequence
When this mode is activated, the ICEPick TAP is no longer visible. The selected secondary
TAPs are connected between the device TDI and TDO. Although the ICEPick TAP is not
visible, it continues to advance state in step with the other selected TAPs. In this sense it is
a shadow TAP. When in the Run Test Idle state, a special address can be scanned that will
make the ICEPick TAP visible again.
011
Disappear-forever
Once activated, the ICEPick TAP is no longer visible between the device TDI and TDO.
Only a power-on reset will make the TAP visible again.
100
Reserved
Reserved (behaves like Always-first)
101
Reserved
Reserved (behaves like Always-first)
110
Key Sequence with
This mode operates in the same manner as the KeySequence mode except that any values
Forwarding
shifted in during the Run Test Idle state are driven out the device TDO. The device TDO
pin is driven during RunTest Idle.
111
Reserved
Reserved (behaves like Always-first)
27.2.4.6.3.1.2 Debug TAP Linking Control Block
The debug TAP linking block contains the control and status registers used in the selection of secondary
TAPs into the master scan path. Up to 16 secondary TAPs can be supported. Each TAP has its own
debug TAP control and status register.
3602
Debug and Emulation
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated