Powerquicc Ii Restrictions; Nonscan Chain Operation - Freescale Semiconductor MPC8260 PowerQUICC II Family Reference Manual

Code
B7 B6 B5 B4 B3 B2 B1 B0
1 1 1 1 0
1 1 1 1 0
1
B0 (lsb) is shifted first.
The parallel output of the instruction register is set to all ones in the test-logic-reset controller state. Notice
that this preset state is equivalent to the BYPASS instruction. During the capture-IR controller state, the
parallel inputs to the instruction shift register are loaded with the CLAMP command code.
13.5

PowerQUICC II Restrictions

The control afforded by the output enable signals using the boundary-scan register and the EXTEST
instruction requires a compatible circuit-board test environment to avoid device-destructive
configurations. The user must avoid situations in which the PowerQUICC II's output drivers are enabled
into actively driven networks.
13.6

Nonscan Chain Operation

In nonscan chain operation, the TCK input does not include an internal pull-up resistor and should be tied
high or low to preclude mid-level inputs.
To ensure that the scan chain test logic is kept transparent to the system logic, the TAP controller is forced
into the test-logic-reset state. This is done inside the chip by connecting TRST to PORESET
TMS should remain logic high, so that the TAP controller does not leave the test-logic-reset state.
Freescale Semiconductor
Table 13-2. Instruction Decoding (continued)
1
Instruction
0 0 0 HI–Z
0 0 1 CLAMP and
BYPASS
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Description
Provided as a manufacturer's optional public instruction to
avoid back driving the output pins during circuit-board testing.
When HI-Z is invoked all output drivers, including the two-state
drivers, are turned off (high impedance). The instruction
selects the bypass register.
CLAMP selects the single-bit bypass register as shown in the
BYPASS instruction figure above, and the state of all signals
driven from the system output pins is completely defined by the
data previously shifted into the boundary scan register. For
example, using the SAMPLE/PRELOAD instruction.
IEEE 1149.1 Test Access Port
13-7