AMD-K6 Datasheet, PDF (223/346 Pages) Advanced Micro Devices – AMD-K6 Processor

20695H/0—March 1998
Preliminary Information
AMD-K6^® Processor Data Sheet
11.3
Boundary-Scan Test Access Port (TAP)
Test Access Port
TAP Signals
The boundary-scan Test Access Port (TAP) is an IEEE standard
that defines synchronous scanning test methods for complex
logic circuits, such as boards containing a processor. The
AMD-K6 processor supports the TAP standard defined in the
IEEE Standard Test Access Port and Boundary-Scan Architecture
(IEEE 1149.1-1990) specification.
Boundary scan testing uses a shift register consisting of the
serial interconnection of boundary-scan cells that correspond
to each I/O buffer of the processor. This non-inverting register
chain, called a Boundary Scan Register (BSR), can be used to
capture the state of every processor pin and to drive every
processor output and bidirectional pin to a known state.
Each BSR of every component on a board that implements the
boundary-scan architecture can be serially interconnected to
enable component interconnect testing.
The TAP consists of the following:
s Test Access Port (TAP) Controller—The TAP controller is a
synchronous, finite state machine that uses the TMS and
TDI input signals to control a sequence of test operations.
See “TAP Controller State Machine” on page 212 for a list
of TAP states and their definition.
s Instruction Register (IR)—The IR contains the instructions
that select the test operation to be performed and the Test
Data Register (TDR) to be selected. See “TAP Registers” on
page 206 for more details on the IR.
s Test Data Registers (TDR)—The three TDRs are used to
process the test data. Each TDR is selected by an
instruction in the Instruction Register (IR). See “TAP
Registers” on page 206 for a list of these registers and their
functions.
The test signals associated with the TAP controller are as
follows:
s TCK—The Test Clock for all TAP operations. The rising edge
of TCK is used for sampling TAP signals, and the falling
edge of TCK is used for asserting TAP signals. The state of
the TMS signal sampled on the rising edge of TCK causes
Chapter 11
Test and Debug
205