
26
AMD-K5 Processor
AMD K86 Family BIOS and Software Tools Developers Guide
21062E/0—June 1997
Preliminary Information
Test Access Port
(TAP) BIST
The TAP BIST performs all the functions of the normal BIST, up
to and including the PLA signature test, in the exact manner as
the normal BIST. However, after the PLA test, the test result is
not transferred to the EAX register.
The TAP BIST is started by loading and executing the
RUNBIST instruction in the test access port, as described in
“Boundary Scan Architecture Support” on page 41. When the
RUNBIST instruction is executed, the processor enters into a
reset mode that is identical to that entered when the RESET
signal is asserted. Upon completion of the TAP BIST, the result
remains in the BIST result register for shifting out through the
TDO signal. The TRST signal must be asserted, or the TAP
instruction must be changed, to exit TAP BIST and return to
normal operation.
Output-Float Test
The Output-Float Test mode is entered if FLUSH is asserted
before the falling edge of RESET. This causes the processor to
place all of its output and bidirectional signals in the
high-impedance state. In this isolated state, system board
traces and connections can be tested for integrity and
driveability. The Output-Float Test mode can only be exited by
asserting RESET again.
On the AMD-K5 processor and Pentium, FLUSH# is an
edge-triggered interrupt. On the 486 processor, however, the
signal is a level-sensitive input.
6
5
4
3
2
1
0
No Error
No Error
No Error
No Error
No Error
No Error
No Error
Instruction-cache linear tags
Data-cache linear tags
PLA
Microcode ROM
Data-cache data
Instruction cache physical tags
Data-cache physical tags
Table 12. BIST Error Bit Definition in EAX Register (continued)
Bit Number
Bit Value
0
1