IEEE 1149.1-Compliant Interface (JTAG)
MPC561/MPC563 Reference Manual, Rev. 1.2
25-32
Freescale Semiconductor
25.1.3.4
CLAMP
The CLAMP instruction selects the single-bit bypass register as shown in
, and the state of all
signals driven from system output pins is completely defined by the data previously shifted into the
boundary scan register (for example, using the SAMPLE/PRELOAD instruction).
25.1.4
HI-Z
The HI-Z instruction is provided as a manufacturer’s optional public instruction to prevent having to
backdrive the output pins during circuit-board testing. When HI-Z is invoked, all output drivers, including
the two-state drivers, are turned off (i.e., high impedance). The instruction selects the bypass register.
25.2
MPC561/MPC563 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 MPC561/MPC563 output drivers are enabled
into actively driven networks.
The MPC561/MPC563 features a low-power stop mode. The interaction of the scan chain interface with
low-power stop mode is as follows:
1. The TAP controller must be in the test-logic-reset state to either enter or remain in the low-power
stop mode. Leaving the TAP controller in the test-logic-reset state negates the ability to achieve
low-power, but does not otherwise affect device functionality.
2. The TCK input is not blocked in low-power stop mode. To consume minimal power, the TCK input
should be externally connected to V
DD
or ground.
3. The TMS pin includes an on-chip pull-up resistor. In low-power stop mode, this pin should remain
either unconnected or connected to VDD to achieve minimal power consumption. Note that for
proper reset of the scan chain test logic, the best approach is to pull JCOMP low at power-on reset
(PORESET).
4. JCOMP must be low prior to PORESET assertion after low power mode exits otherwise an
unknown state will occur.
25.2.1
Non-Scan Chain Operation
In non-scan chain operation, there are two constraints. First, the TCK input does not include an internal
pull-up resistor and should not be left unconnected to preclude mid-level inputs. The second constraint is
to ensure that the scan chain test logic is kept transparent to the system logic by forcing TAP into the
test-logic-reset controller state, using either of two methods. Connecting pin JCOMP to logic 0 (or one of
the reset pins), or TMS must be sampled as a logic one for five consecutive TCK rising edges. If then TMS
either remains unconnected or is connected to V
DD
, then the TAP controller cannot leave the
test-logic-reset state, regardless of the state of TCK.
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...