SCANSTA111 National Semiconductor Corporation, SCANSTA111 Datasheet - Page 3

• Manufacturer Part Number: SCANSTA111
• Description: Enhanced Scan Bridge Multidrop Addressable Ieee 1149.1 Jtag Port
• Manufacturer: National Semiconductor Corporation

Architecture
Figure 1 shows the basic architecture of the ’STA111. The
device’s major functional blocks are illustrated here. The
TAP Controller, a 16-state state machine, is the central con-
trol for the device. The instruction register and various test
data registers can be scanned to exercise the various func-
tions of the ’STA111 (these registers behave as defined in
IEEE Std. 1149.1). The ’STA111 selection controller provides
the functionality that allows the 1149.1 protocol to be used in
a multi-drop environment. It primarily compares the address
FIGURE 1. SCANSTA111 Block Diagram
3
input to the slot identification and enables the ’STA111 for
subsequent scan operations. The Local Scan Port Network
(LSPN) contains multiplexing logic used to select different
port configurations. The LSPN control block contains the
Local Scan Port Controllers (LSPC) for each Local Scan Port
(LSP
the ’STA111 instruction register, mode registers, and the TAP
controller. Each local port contains all four boundary scan
signals needed to interface with the local TAPs plus the
optional Test Reset signal (TRST).
0
, LSP
1
... LSP
n
). This control block receives input from
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