SCANPSC110FDMQB datasheet(5/29 Pages) NSC

5 / 29 page

Overview of SCANPSC110F Bridge

Functions (Continued)

In multi-drop scan systems, a scan tester can select indi-

vidual ’PSC110Fs for participation in upcoming scan opera-

tions. ’PSC110F “selection” is accomplished by simulta-

neously scanning a device address out to multiple

’PSC110Fs. Through an on-chip address matching process,

only those ’PSC110Fs whose statically-assigned address

matches the scanned-out address become selected to re-

ceive further instructions from the scan tester. ’PSC110F se-

lection is done using a “Level-1” protocol, while follow-on in-

structions are sent to selected ’PSC110Fs by using a

“Level-2” protocol.

The

’PSC110F

contains

three

distinct

but

coupled

state-machines (see

Figure 2 ). The first of these is the

TAP-control state-machine, which is used to drive the

’PSC110Fs scan ports in conformance with the 1149.1 Stan-

dard (see

Figure 17 of appendix). The second is the

’PSC110F-selection state-machine (

Figure 3). The third

state-machine actually consists of three identical but inde-

pendent state-machines (see

Figure 4), one per ’PSC110F

local

scan

port.

Each

these

scan

port-selection

state-machines allows individual local ports to be inserted

into and removed from the ’PSC110Fs overall scan chain.

The ’PSC110F selection state-machine performs the ad-

dress matching which gives the ’PSC110F its multi-drop ca-

pability. That logic supports single-’PSC110F access,

multi-cast,

and

broadcast.

The

’PSC110F-selection

state-machine implements the chip’s Level-1 protocol.

DS100327-4

FIGURE 2. SCANPSC110F Bridge State Machines

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