AMD-K6-2E Datasheet, PDF (254/332 Pages) Advanced Micro Devices – AMD-K6™-2E Embedded Processor

AMD-K6™-2E Processor Data Sheet
Preliminary Information
22529B/0—January 2000
TAP Controller State
Machine
SAMPLE/PRELOAD Instruction. The SAMPLE/PRELOAD instruction
performs two functions. These functions are as follows:
s During the Capture-DR state, the processor loads the BSR
shift register with the current state of every input, output,
and bidirectional pin.
s During the Update-DR state, the BSR output register is
loaded from the BSR shift register in preparation for the
next EXTEST instruction.
The SAMPLE/PRELOAD instruction does not affect the normal
operational state of the processor.
BYPASS Instruction. The BYPASS instruction selects the BR
register, which reduces the boundary-scan length through the
processor from 281 to one (TDI to BR to TDO). The BYPASS
instruction does not affect the normal operational state of the
processor.
IDCODE Instruction. The IDCODE instruction selects the DIR
register, allowing the device identification code to be shifted
out of the processor. This instruction is loaded into the IR when
the TAP controller is reset. The IDCODE instruction does not
affect the normal operational state of the processor.
HIGHZ Instruction. The HIGHZ instruction forces all output and
bidirectional pins to be floated. During this instruction, the BR
is selected and the normal operational state of the processor is
not affected.
The TAP controller state diagram is shown in Figure 82 on page
237. State transitions occur on the rising edge of TCK. The logic
0 or 1 next to the states represents the value of the TMS signal
sampled by the processor on the rising edge of TCK.
236
Test and Debug
Chapter 12