MOTOROLA
Chapter 24. IEEE 1149.1-Compliant Interface (JTAG)
24-21
IEEE 1149.1 Test Access Port
1.Bi-state outputs (Pin Function = O) such as mdo_2, and mdo_3, are incorporated with general I/O pads hard-wired to
keep output enable always on in system mode. The JTAG Control cell, indicated by the next lower bsdl bit in the
chain, is configured as an “internal” only cell to be held at a “1” value (always driving out) during JTAG testing.
2. Some input-only cells made with generic I/O pads are configured with “internal” control cells to keep them always in
input mode, such as epee, b0epee, and input pins that may be attached to analog references. Other input-only cells
are configured as bidirectional for JTAG testing, to give the board-level ATPG tools the flexability to use the pad as
an input or output, depending on the network of other devices that the pin is connected too. If it is desired to restrict
these pins to only act as receivers during JTAG mode, then these JTAG bsdl entries can be converted as shown in
the example below:
3. This description allows ATPG tools to use a pin as a driver or receiver:
4. A modification to restrict ATPG tools to use a functional input-only pin as an input receiver only:
.
5. The PORESET, HRESET, and SRESET pins are not part of the JTAG boundary scan chain. These pins are used in
the reset configuration to enter JTAG. Board-level connections to them will not be testable with the EXTEST and
CLAMP instructions. They do respond to the HI-Z JTAG instruction for parametric testing purposes.6.
6. The XTAL, EXTAL, and XFC pins are associated with analog signals and are excluded from the boundary scan chain.
7. The READI module reset pin, rsti_b, (bsdl pin 517) is in the JTAG boundary scan chain, but must be kept at a “0” level
during JTAG testing, (except for Hi-Z testing), due to system interactions. It is classified as a “l(fā)inkage” pin, and its data
and control cells are configured to advise ATPG tools to drive a “0” value in during JTAG testing.
8. Pad type naming conventions:
–26 V – 2.6 V
–5 V – 5 V
–s – slow
–f – fast
–h – high drive
–
a – analog input
–
i – input only
–
d – has direct connection to the pad (may be used for module test)
–
r – resized cell instance
9. Column Descriptions:
–
Columns 1 through 8 are entries from the boundary-scan description from the BSDL file. The columns
and formats for each of these entries are defined in the IEEE Std. 1149.1b-1994 Supplement to the
516
BC_2
*
internal
0
517
BC_4
* [rsti_b force to 0]
internal
0
I
26v
518
BC_2
*
controlr
0
519
BC_7
evti_b
bidir
0
518
0
Z
I
26v
188
BC_2
*
controlr
0
189
BC_7
irq6_b_modck2
bidir
0
188
0
Z
I
26v
188
BC_2
*
internal
0
189
BC_4
irq6_b_modck2
input
X
I
26v
Table 24-1. Boundary Scan Bit Definition (continued)
BSDL
Bit
Cell
Type
Port Name
BSDL
Function
saf.
val.
cnt.
cell
dis.
val.
rslt
Pin
Function
Pad
Type