1FEATURES
2• True IEEE 1149.1 Hierarchical and Multidrop
Addressable Capability
• The 8 Address Inputs Support up to 249
Unique Slot Addresses, an Interrogation
Address, Broadcast Address, and 4 Multi-Cast
Group Addresses (Address 000000 is
Reserved)
• 7 IEEE 1149.1-Compatible Configurable Local
Scan Ports
• Bi-directional Backplane and LSP0 Ports are
Interchangeable Slave Ports
• Capable of Ignoring TRST of the Backplane
Port when it Becomes the Slave.
• Stitcher Mode Bypasses Level 1 and 2
Protocols
• Mode Register0 Allows Local TAPs to be
Bypassed, Selected for Insertion into the Scan
Chain Individually, or Serially in Groups of
Two or Three
• Transparent Mode can be Enabled with a
Single Instruction to Conveniently Buffer the
Backplane IEEE 1149.1 Pins to Those on a
Single Local Scan Port
• General Purpose Local Port Pass Through Bits
are Useful for Delivering Write Pulses for Flash
Programming or Monitoring Device Status.
• Known Power-Up State
• TRST on all Local Scan Ports
• 32-bit TCK Counter
• 16-bit LFSR Signature Compactor
• Local TAPs can Become TRI-STATE via the OE
Input to Allow an Alternate Test Master to Take
Control of the Local TAPs (LSP0-3 have a TRISTATE
Notification Output)
• 3.0-3.6V VCC Supply Operation
• Supports Live Insertion/Withdrawal

DESCRIPTION
The SCANSTA112 extends the IEEE Std. 1149.1 test
bus into a multidrop test bus environment. The
advantage of a multidrop approach over a single
serial scan chain is improved test throughput and the
ability to remove a board from the system and retain
test access to the remaining modules. Each
SCANSTA112 supports up to 7 local IEEE1149.1
scan chains which can be accessed individually or
combined serially.
Addressing is accomplished by loading the instruction
register with a value matching that of the Slot inputs.
Backplane and inter-board testing can easily be
accomplished by parking the local TAP Controllers in
one of the stable TAP Controller states via a Park
instruction. The 32-bit TCK counter enables built in
self test operations to be performed on one port while
other scan chains are simultaneously tested.
The STA112 has a unique feature in that the
backplane port and the LSP0 port are bidirectional.
They can be configured to alternatively act as the
master or slave port so an alternate test master can
take control of the entire scan chain network from the
LSP0 port while the backplane port becomes a slave.