
July 2004 
AS91L1006BU
AS91L1006BU Gateway Functional Description 
The basic structure of the AS91L1006BU 
device is shown in Figure-1. The core of the device 
is the 16-state IEEE1149.1 TAP controller state 
machine. All accesses to the internal registers of 
the AS91L1006BU device are controlled via this 
state machine during normal operation as per the 
IEEE1149.1 standard. The address selection logic 
enables the AS91L1006BU to operate in a Multi-
Drop environment within system backplane. 
The address selection logic compares the 
scanned address to the slot address value 
presented on the I/O of the AS91L1006BU device. 
The LSP park/unpark logic provides control 
through instructions scanned in under the 
IEEE1149.1 protocol, to select, which LSP will be 
placed into the active, scan chain. The pass-
through and LSP connection logic selects the 
signal paths for the LSP IEEE1149.1 signals. The 
device also supports a Pass-Through mode which 
enables the primary IEEE1149.1 signals to be 
routed to any of the LSPs. This signal routing is 
selectable via I/O pins on the AS91L1006BU 
device. 
Figure-2 shows the device selection state 
machine. The AS91L1006BU will perform an 
address compare on the slot address presented 
at its I/O and the value scanned in via the 
IEEE1149.1. If the value matches then the 
AS91L1006BU becomes selected and is ready for 
normal access via IEEE1149.1 commands. If the 
address does not match then the device will 
proceed to the unselected mode, where it will 
remain until the AS91L1006BU is issued a 
GOTOWAIT instruction or a reset occurs via 
TRST or the LSP_RESET pin. 
Selected Single
Device
Device
Unselected
Select Group
of Devices
Select All
Devices
Wait for
Selection
Parked-TLR
Parked-RTI
Parked-
PauseIR
UnParked
Parked-
PauseDR
Figure 2 - AS91L1006BU 
Selection Logic State machine 
Figure 3 - The LSP  
Park/Unpark State Machine 
The LSP Park/Unpark State Machine controls the insertion of the LSPs into the current active scan 
chain. The ability to park the LSP in certain IEEE1149.1 states, enable the AS91L1006BU to perform 
several functions including backplane interconnect testing and IC BIST. 
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