Pin Name

Description

No.

Pins

I/O

TRIST

TRIST

(01-03)

5

O

TRI-STATE NOTIFICATION OUTPUT: This signal is asserted high when the associated

TDO is TRI-STATEd. Associated means TRIST

This output has 12mA of drive current.

A0

A1

B1

4

I

BACKPLANE PASS-THROUGH INPUT: A general purpose input which is driven to the Y

a single selected LSP. (Not available when multiple LSPs are selected). This input has a

25K

Ω internal pull-up resistor. MPsel

port and which is LSP

Y0

Y1

B1

4

O

BACKPLANE PASS-THROUGH OUTPUT: A general purpose output which is driven from

the A

TRI-STATE output has 12mA of drive current. MPsel

master backplane port and which is LSP

S

(0-7)

8

I

SLOT IDENTIFICATION: The configuration of these pins is used to identify (assign a unique

address to) each ’STA112 on the system backplane

OE

1

I

OUTPUT ENABLE for the Local Scan Ports, active low. When high, this active-low control

signal TRI-STATEs all local scan ports on the ’STA112, to enable an alternate resource to

access one or more of the local scan chains.

TDO

(01-06)

6

O

TEST DATA OUTPUTS: Individual output for each of the local scan ports . These

TRI-STATE outputs have 12mA of drive current.

TDI

(01-06)

6

I

TEST DATA INPUTS: Individual scan data input for each of the local scan ports. This input

has a 25K

Ω internal pull-up resistor.

TMS

(01-06)

6

O

TEST MODE SELECT OUTPUTS: Individual output for each of the local scan ports. TMS

n

does not provide a pull-up resistor (which is assumed to be present on a connected TMS

input, per the IEEE 1149.1 requirement) . These TRI-STATE outputs have 24mA of drive

current.

TCK

(01-06)

6

O

LOCAL TEST CLOCK OUTPUTS: Individual output for each of the local scan ports. These

are buffered versions of TCK

TRST

(01-06)

6

O

LOCAL TEST RESETS: A gated version of TRST

of drive current.

A0

2

I

LOCAL PASS-THROUGH INPUTS: General purpose inputs which can be driven to the

backplane pin Y

These inputs have a 25K

Ω internal pull-up resistor.

Y0

2

O

LOCAL PASS-THROUGH OUTPUT: General purpose outputs which can be driven from the

backplane pin A

These TRI-STATE outputs have 12mA of drive current.

Note 1: Refer to the IBIS model on our website for I/O characteristics.

Application Overview

ADDRESSING SCHEME

The SCANSTA112 architecture extends the functionality of

the IEEE 1149.1 Standard by supplementing that protocol

with an addressing scheme which allows a test controller to

communicate with specific ’STA112s within a network of

’STA112s. That network can include both multi-drop and

hierarchical connectivity. In effect, the ’STA112 architecture

allows a test controller to dynamically select specific portions

of such a network for participation in scan operations. This

allows a complex system to be partitioned into smaller

blocks for testing purposes. The ’STA112 provides two levels

of test-network partitioning capability. First, a test controller

can select individual ’STA112s, specific sets of ’STA112s

(multi-cast groups), or all ’STA112s (broadcast). This

’STA112-selection process is supported by a Level-1 com-

munication protocol. Second, within each selected ’STA112,

a test controller can select one or more of the chip’s seven

local scan-ports. That is, individual local ports can be se-

lected for inclusion in the (single) scan-chain which a

’STA112 presents to the test controller. This mechanism

allows a controller to select specific scan-chains within the

overall scan network. The port-selection process is sup-

ported by a Level-2 protocol.

HIERARCHICAL SUPPORT

Multiple SCANSTA112’s can be used to assemble a hierar-

chical boundary-scan tree. In such a configuration, the sys-

tem tester can configure the local ports of a set of ’STA112s

so as to connect a specific set of local scan-chains to the

active scan chain. Using this capability, the tester can selec-

tively communicate with specific portions of a target system.

The tester’s scan port is connected to the backplane scan

port of a root layer of ’STA112s, each of which can be

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