PI7C8150AND datasheet(101/111 Pages) PERICOM

101 / 111 page

PI7C8150A

2-PORT PCI-TO-PCI BRIDGE

Page 101 of 111

APRIL 2006 – Revision 1.1

The instruction determines the test to be performed, the test data register to be accessed, or

both. The IR is two bits wide. When the IR is selected, the most significant bit is connected

to TDI, and the least significant bit is connected to TDO. The value presented on the TDI

pin is shifted into the IR on each rising edge of TCK. The TAP controller captures fixed

parallel data (1101 binary). When a new instruction is shifted in through TDI, the value

1101(binary) is always shifted out through TDO, least significant bit first. This helps

identify instructions in a long chain of serial data from several devices.

Upon activation of the TRST_L reset pin, the latched instruction asynchronously changes

to the id code instruction. When the TAP controller moves into the test state other than by

reset activation, the opcode changes as TDI shifts, and becomes active on the falling edge

of TCK.

16.2

BOUNDARY SCAN INSTRUCTION SET

The PI7C8150A supports three mandatory boundary-scan instructions (BYPASS,

SAMPLE and EXTEST). The table shown below lists the PI7C8150A’s boundary-scan

instruction codes.

Table 16-1. TAP Pins

Instruction

Requisite

Opcode (binary)

Description

EXTEST

IEEE 1149.1

Required

00000

EXTEST initiates testing of external circuitry, typically board-

level interconnects and off chip circuitry. EXTEST connects the

boundary-scan register between TDI and TDO. When EXTEST

is selected, all output signal pin values are driven by values

shifted into the boundary-scan register and may change only of

the falling edge of TCK. Also, when EXTEST is selected, all

system input pin states must be loaded into the boundary-scan

SAMPLE

IEEE 1149.1

Required

0001

SAMPLE performs two functions:

A snapshot of the sample instruction is captured on the

rising edge of TCK without interfering with normal

operation. The instruction causes boundary-scan register

cells associated with outputs to sample the value being

driven.

On the falling edge of TCK, the data held in the boundary-

scan cells is transferred to the slave register cells.

Typically, the slave latched data is applied to the system

outputs via the EXTEST instruction.

INTSCAN

00010

Enable internal SCAN test

CLAMP

00100

CLAMP instruction allows the state of the signals driven from

component pins to be determined from the boundary-scan

between TDI and TDO. The signal driven from the component

pins will not change while the CLAMP instruction is selected.

BYPASS

11111

BYPASS instruction selects the one-bit bypass register between

TDI and TDO pins. 0 (binary) is the only instruction that

accesses the bypass register. While this instruction is in effect,

all other test data registers have no effect on system operation.

Test data registers with both test and system functionality

performs their system functions when this instruction is selected.

06-0057

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