SCANSTA111

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SNLS060K – AUGUST 2001 – REVISED APRIL 2013

Figure 4. Local SCANSTA111 Port Configuration State Machine

The 'STA111's scan port-configuration state-machine is used to control the insertion of local scan ports into the

overall scan chain, or the isolation of local ports from the chain. From the perspective of a system's (single) scan

controller, each 'STA111 presents only one scan chain to the master. The 'STA111 architecture allows one or

more of the 'STA111's local ports to be included in the active scan chain.

Each local port can be parked in one of four stable states (Parked-TLR, Parked-RTI, Parked-Pause-DR or

Parked-Pause-IR), either individually or simultaneously with other local ports. Parking a chain removes that local

chain from the active scan chain. Conversely, a parked chain can be unparked, causing the corresponding local

port to be inserted into the active scan chain.

As shown in Figure 4, the 'STA111's three scan port-configuration state-machines allow each of the part's local

ports to occupy a different state at any given time. For example, some ports may be parked, perhaps in different

states, while other ports participate in scan operations. The state-diagram shows that some state transitions

depend on the current state of the TAP-control state-machine. As an example, a local port which is presently in

the Parked-RTI state does not become unparked (i.e., enter the Unparked state) until the 'STA111 receives an

UNPARK instruction and the 'STA111's TAP state-machine enters the Run-Test/Idle state.

Similarly, certain transitions of the scan port-configuration state-machine can force the 'STA111's LSP-control

state-machine into specific states. For example, when a local port is in the Unparked state, the 'STA111 receives

the PARKRTI instruction and the TAP is transitioned through Run-Test/Idle state, the Local Port controller enters

instruction has been updated into the instruction register the TAP MUST be transitioned through the Run-

RTI TAP controller state in this example).

The 'STA111's scan port-configuration state-machine implements part of the 'STA111's Level-2 protocol. In

addition, the 'STA111 provides a number of Level-2 instructions for functions other than local scan port

configuration. These instructions provide access to and control of various registers within the 'STA111. This set

of instructions includes:

BYPASS

CNTRSEL

EXTEST

LFSRON

SAMPLE/PRELOAD

LFSROFF

IDCODE

CNTRON

MODESEL

CNTROFF

MCGRSEL

GOTOWAIT

LFSRSEL

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