Motorola MCF5282, MCF5281 Testleakage Instruction, Enabletestctrl Instruction, Highz Instruction

Functional Description

contains the $2 opcode. The sampled data is accessible by shifting it through the boundary scan register to the TDO output by using the shift-DR state. Both the data capture and the shift operation are transparent to system operation.

NOTE

External synchronization is required to achieve meaningful results because there is no internal synchronization between TCLK and the system clock.

•PRELOAD - initialize the boundary scan register update cells before selecting EXTEST or CLAMP. This is achieved by ignoring the data shifting out on the TDO pin and shifting in initialization data. The update-DR state and the falling edge of TCLK can then transfer this data to the update cells. The data is applied to the external output pins by the EXTEST or CLAMP instruction.

31.5.3.4 TEST_LEAKAGE Instruction

The TEST_LEAKAGE instruction forces the jtag_leakage output signal to high. It is intended to tri-state all output pad buffers and disable all of the part’s pad input buffers except TEST and TRST. The jtag_leakage signal is asserted at the rising edge of TCLK when the TAP controller transitions from update-IR to run-test/idle state. Once asserted, the part disables the TCLK, TMS, and TDI inputs into JTAG and forces these JTAG inputs to logic 1. The TAP controller remains in the run-test/idle state until the TRST input is asserted (logic 0).

31.5.3.5 ENABLE_TEST_CTRL Instruction

The ENABLE_TEST_CTRL instruction selects a 3-bit shift register (TEST_CTRL) for connection as a shift path between the TDI and TDO pin. When the user transitions the TAP controller to the UPDATE_DR state, the register transfers its value to a parallel hold register. It allows the control chip to test functions independent of the JTAG TAP controller state.

31.5.3.6 HIGHZ Instruction

The HIGHZ instruction eliminates the need to backdrive the output pins during circuit-board testing. HIGHZ turns off all output drivers, including the 2-state drivers, and selects the bypass register. HIGHZ also asserts internal reset for the MCU system logic to force a predictable internal state.

31.5.3.7 LOCKOUT_RECOVERY Instruction

If a user inadvertently enables security on a MCU, the LOCKOUT_RECOVERY instruction allows the disabling of security by the complete erasure of the internal flash contents including the configuration field. This does not compromise security as the entire

31-10 MCF5282 User’s Manual MOTOROLA