STMicroelectronics SPC572L series Reference Manual page 1791

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60.7.8.3 Scan Formats
60.7.8.3.1 Overview
Scan formats utilizing the Advanced Protocol address different use cases. The amount of
information transferred per TAPC state is based on the constraints imposed by these use
cases. In one extreme two types of control information, the first allowing the stall of the
completion of the Scan Packet, and the second supporting the Wire-AND of TAP.7 controller
output are added to the TMS, TDI, and TDO information within the Scan Packet. In the
other extreme, the external tool may minimize the information transferred for each TAPC
state using its understanding of the application and transfer only the data of interest. In
some cases the transfer of only one bit of information per TAPC is required. There are a
number of scan formats that operate between these two extremes. The external tool
chooses a scan format that best matches the performance/functionality needs of the
application.
The scan formats added to specify the use of the Advance Protocol are listed below:
•
MScan – Maximum flexibility.
•
OScan0-7 – Optimized for test and debug applications.
These scan formats provide seven different functions. Five factors have influenced the
definition of these scan formats:
•
Supporting the capabilities of the IEEE1149.x and IEEE 1532 Standards.
•
Providing the STL and external tool an opportunity to stall the TAPC state progression.
•
Providing a minimum pin count and scalable functionality.
•
Maximizing the efficiency of scan operations utilized for applications debug operations.
•
Providing a rich set of capability for high end applications debug.
The performance and flexibility of MScan and OScan scan formats are shown in
and Table
subjective/approximate ratings in these tables. These ratings range from least to best. Use
cases for these scan formats are also included in these tables.
60.7.8.3.2 MScan scan formats
The MScan scan format provides a universal scan function. It is the most flexible but
lowest-performance scan format. The Scan Packets used by these scan formats are
packed with data and control information and is the same for all TAPC states. This scan
format accommodates the deployment of IEEE 1149.1 IP with non-compliant behavior
within the STL. The STL is allowed to stall the TAPC state progression (to pace the arrival of
Scan Packets with its ability to process them), and uses Wire-ANDed Output.
IEEE 1149.7 Compact JTAG Test Access Port Controller (CJTAG)
996, respectively. The performance and flexibility of these scan formats are given
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