SCANPSC110 datasheet(7/29 Pages) NSC

7 / 29 page

Overview of SCANPSC110F Bridge

Functions (Continued)

ample, a local port which is presently in the

Parked-RTI state

does not become unparked (i.e., enter the

Unparked state)

until the ’PSC110F receives an

UNPARK instruction and the

’PSC110F’s TAP state-machine enters the

Run-Test/Idle

state.

Similarly, certain transitions of the scan port-configuration

state-machine

can

force

the

’PSC110F’s TAP-control

state-machine into specific states. For example, when a lo-

cal port is in the

Unparked state and the ’PSC110F receives

a PARKRTI instruction, the Local Port controller enters the

Parked-RTI state in which TMS

Ln will be held low until the

port is later unparked. While TMS

Ln is held low, all devices

on that local scan chain remain in their current TAP State

(the

RTI TAP controller state in this example).

The ’PSC110F’s scan port-configuration state-machine

implements part of the ’PSC110F’s Level-2 protocol. In addi-

tion, the ’PSC110F provides a number of Level-2 instructions

for functions other than local scan port confguration. These

instructions provide access to and control of various regis-

ters within the ’PSC110F. This set instructions includes:

BYPASS

CNTRSEL

EXTEST

LFSRON

SAMPLE/PRELOAD

LFSROFF

IDCODE

CNTRON

MODESEL

CNTROFF

MCGRSEL

GOTOWAIT

LFSRSEL

Figure 5 illustrates how the ’PSC110F’s state-machines in-

teract. The ’PSC110F-selection state-machine enables or

disables

operation

the

chip’s

three

port-selection

state-machines. In ’PSC110Fs which are selected via

Level-1 protocol (either as individual ’PSC110Fs or as mem-

bers of broadcast or multi-cast groups), Level-2 protocol

commands can be used to park or unpark local scan ports.

Note

that

most

transitions

the

port-configuration

state-machines are gated by particular states of the

’PSC110F’s TAP-control state-machine, as shown in

Figures

4, 5.

DS100327-6

FIGURE 5. Relationship Between SCANPSC110F Bridge State Machines

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