Signal Description
ARM7TDMI Data Sheet
ARM DDI 0029E
2-10
O
SHCLKBS
Boundary scan shift clock,
phase 1
04
This control signal is provided to ease the connection of an
external boundary scan chain.
SHCLKBS
is used to clock the
master half of the external scan cells. When in the SHIFT-DR
state of the state machine and scan chain 3 is selected,
SHCLKBS
follows
TCK1
. When not in the SHIFT-DR state or
when scan chain 3 is not selected, this clock is LOW. When an
external boundary scan chain is not connected, this output
should be left unconnected.
SHCLK2BS
Boundary scan shift clock,
phase 2
04
This control signal is provided to ease the connection of an
external boundary scan chain.
SHCLK2BS
is used to clock the
master half of the external scan cells. When in the SHIFT-DR
state of the state machine and scan chain 3 is selected,
SHCLK2BS
follows
TCK2
. When not in the SHIFT-DR state or
when scan chain 3 is not selected, this clock is LOW. When an
external boundary scan chain is not connected, this output
should be left unconnected.
TAPSM[3:0]
TAP controller
state machine
04
This bus reflects the current state of the TAP controller state
machine, as shown in
·
8.4.2 The JTAG state machine
on
page 8-8
. These bits change off the rising edge of
TCK
.
TBE
Test Bus Enable.
IC
When driven LOW,
TBE
forces the data bus
D[31:0]
, the
Address bus
A[31:0]
, plus
LOCK
,
MAS[1:0]
,
nRW
,
nTRANS
and
nOPC
to high impedance. This is as if both
ABE
and
DBE
had both been driven LOW. However,
TBE
does not have an
associated scan cell and so allows external signals to be driven
high impedance during scan testing. Under normal operating
conditions,
TBE
should be held HIGH at all times.
TBIT
O4
When HIGH, this signal denotes that the processor is executing
the THUMB instruction set. When LOW, the processor is
executing the ARM instruction set. This signal changes in phase
2 in the first execute cycle of a BX instruction.
TCK
IC
Test Clock.
TCK1
TCK, phase 1
04
This clock represents phase 1 of
TCK
.
TCK1
is HIGH when
TCK
is HIGH, although there is a slight phase lag due to the internal
clock non-overlap.
TCK2
TCK, phase 2
04
This clock represents phase 2 of
TCK
.
TCK2
is HIGH when
TCK
is LOW, although there is a slight phase lag due to the internal
clock non-overlap.
TCK2
is the non-overlapping compliment of
TCK1
.
TDI
IC
Test Data Input.
TDO
Test Data Output.
O4
Output from the boundary scan logic.
TMS
IC
Test Mode Select.
Name
Type
Description
Table 2-1: Signal Description (Continued)