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SCANPSC110FSC

SCAN Bridge Hierarchical and Multidrop Addressable JTAG Port (IEEE1149.1 System Test Support)

Fairchild Semiconductor 

TABLE 1. Glossary of Terms

LFSR

Linear Feedback Shift Register. When enabled, will generate a 16-bit signature of sampled serial test

data.

LSP

Local

Local Scan Port. A four signal port that drives a “local” (i.e. non-backplane) scan chain.

(e.g., TCKL1, TMSL1, TDOL1, TDIL1)

Local is used to describe IEEE Std. 1149.1 compliant scan rings and the SCANPSC110F Bridge Test

Access Port that drives them. The term “local” was adopted from the system test architecture that the

SCANPSC110F Bridge will most commonly be used in; namely, a system test backplane with a

SCANPSC110F Bridge on each card driving up to 3 “local” scan rings per card. (Each card can contain

multiple SCANPSC110Fs, with 3 local scan ports per SCANPSC110F.)

Park/Unpark

Park, parked, unpark, and unparked, are used to describe the state of the LSP controller and the state

of the local TAP controllers (the “local TAP controllers” refers to the TAP controllers of the scan compo-

nents that make up a local scan ring). Park is also used to describe the action of parking a LSP (transi-

tioning into one of the Parked LSP controller states). It is important to understand that when a LSP

controller is in one of the parked states, TMSL is held constant, thereby holding or “parking” the local

TAP controllers in a given state.

TAP

Test Access Port as defined by IEEE Std. 1149.1

Selected/Unselected Selected and Unselected refers to the state of the SCANPSC110F Bridge Selection Controller. A

selected SCANPSC110F has been properly addressed and is ready to receive Level 2 protocol. Unse-

lected SCANPSC110Fs monitor the system test backplane, but do not accept Level 2 protocol (except

for the GOTOWAIT instruction). The data registers and LSPs of unselected SCANPSC110Fs are not

accessible from the system test master.

Active Scan Chain

The Active Scan Chain refers to the scan chain configuration as seen by the test master at a given

moment. When a SCANPSC110F is selected with all of its LSPs parked, the active scan chain is the

current scan bridge register only. When a LSP is unparked, the active scan chain becomes: TDIB → the

current SCANPSC110F register → the local scan ring registers → a PAD bit → TDOB. Refer to Table 4

for Unparked configurations of the LSP network.

Level 1 Protocol

Level 1 is the protocol used to address a SCANPSC110F.

Level 2 Protocol

Level 2 is the protocol that is used once a SCANPSC110F is selected. Level 2 protocol is IEEE Std.

1149.1 compliant when an individual SCANPSC110F is selected.

PAD

A one bit register that is placed at the end of each local scan port scan-chain. The PAD bit eliminates

the prop delay that would be added by the SCANPSC110F LSPN logic between TDILn and TDOL(n+1)

or TDOB by buffering and synchronizing the TDIL inputs to the falling edge of TCKB, thus allowing data

to be scanned at higher frequencies without violating set-up and hold times.

LSB

Least Significant Bit, the right-most position in a register (bit 0)

MSB

Most Significant Bit, the left-most position in a register

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