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•
Create interrupt request with a break coming from a source
•
Synchronous restart of the system
16.4
JTAG Interface
The JTAG interface is a standardized unit that is typically used for boundary scan and
internal device tests. Because both of these applications are not active during normal
device operation in a system, the JTAG port can be used during normal device operation
as an ideal interface for debugging tasks.
16.5
Device Access Port (DAP)
The cost inferred by each non-functional pin is a strong argument to reduce the tool
access port to as few pins as possible. The standardized Device Access Port (DAP) of
Infineon's latest micro controllers offers a convenient method to get the required
functionality at the least possible cost. With DAP only two pins (DAP0 for the clock, DAP1
for the bidirectional data) are needed to communicate with the tool.
DAP uses a straightforward half-duplex protocol, i.e. the DAP1 pin is used for data
transfer from tool to device and from device to tool at different periods of time while the
clock is provided by the tool to the DAP0 input.
16.5.1
DAP Telegram Format
All information transport between tool and device is done in telegrams. Mandatory 6 bit
CRC check sums assure secure transport even in noisy environments. Splitting
command and reply into separate units transported sequentially allows half-duplex
transmission over a single bidirectional line. The physical interface medium can be
chosen independently as long as the serial bit stream can be transported.
16.5.2
DAP Telegram Catalog
This chapter lists the telegrams implemented by the TC1728. Other telegrams are
silently ignored, resulting in a time-out condition on the tool side.
Three groups of telegrams can be distinguished:
Control Telegrams
These four telegrams are needed to establish and maintain the connection from tool to
device as such. No data is transported.
•
sync - request synchronization pattern
•
turn_off - shut down DAP
•
poll - get the current service request
•
set_maxwait - adjust the parameter for time out
User's Manual
OCDS, V1.5
On-Chip Debug Support (OCDS)
16-13
TC1728
V1.0, 2011-12
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