VSC8221 datasheet(44/138 Pages) MICROSEMI

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VSC8221

Data Sheet

VMDS-10106 Revision 4.1

December 2006

44 of 46

14 TEST MODE INTERFACE (JTAG)

The PHY supports the Test Access Port and Boundary Scan Architecture iEEE 1149.1 standards. The device includes an iEEE

1149.1 compliant test interface, often referred to as a “JTAG TAP interface”. iEEE 1149.1 defined test logic provides the

following standardized test methodologies:

• Testing the interconnections between integrated circuits once they have been assembled onto a printed circuit board or

other substrate.

• Testing the integrated circuit itself during iC and systems manufacture.

• Observing or modifying circuit activity during the component’s normal operation.

The JTAG Test interface logic on the PHY, accessed through a Test Access Port (TAP) interface, consists of a boundary- scan

register and other logic control blocks. The TAP controller includes all iEEE-required signals (TMS, TCK, TDi, and TDO), in

addition to the optional asynchronous reset signal TRST.

The following figure diagrams the TAP and Boundary Scan Architecture.

Figure 15. Test Access Port and Boundary Scan Architecture

The PHY also includes the optional Device identification Register, shown in the following table, which allows the manufacturer,

part number, and version number of the device to be determined through the TAP Controller. See Chapter 11 of the iEEE

1149.1-1990 specifications for more details. Also, note that some of the information in the identification register is duplicated in

the iEEE-specified bit fields in Mii Register 3 (PHY identifier Register #2).

Table 23. JTAG Device identification Register Description

Description

Device Version Number

(or Revision Code)

Part Number

(or Model Number)

Microsemi’s

Manufacturer identity

LSB

Bit Field

31 - 28

27 - 12

11 - 1

Binary Value 0001

1000 0010 0010 0001

001 1001 1000

Boundary-Scan

Device Identification

Bypass Register

Instruction Register,

Instruction Decode,

Control

Test Access Port

Controller

TRSTz

TMS

TDI

TCK

select

control

tdoenable

control

Mux,

DFF

TDO

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