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32072H–AVR32–10/2012
AT32UC3A3
35. Programming and Debugging
35.1
Overview
General description of programming and debug features, block diagram and introduction of main
concepts.
35.2
Service Access Bus
The AVR32 architecture offers a common interface for access to On-Chip Debug, programming,
and test functions. These are mapped on a common bus called the Service Access Bus (SAB),
which is linked to the JTAG port through a bus master module, which also handles synchroniza-
tion between the debugger and SAB clocks.
When accessing the SAB through the debugger there are no limitations on debugger frequency
compared to chip frequency, although there must be an active system clock in order for the SAB
accesses to complete. If the system clock is switched off in sleep mode, activity on the debugger
will restart the system clock automatically, without waking the device from sleep. Debuggers
may optimize the transfer rate by adjusting the frequency in relation to the system clock. This
ratio can be measured with debug protocol specific instructions.
The Service Access Bus uses 36 address bits to address memory or registers in any of the
slaves on the bus. The bus supports sized accesses of bytes (8 bits), halfwords (16 bits), or
words (32 bits). All accesses must be aligned to the size of the access, i.e. halfword accesses
must have the lowest address bit cleared, and word accesses must have the two lowest address
bits cleared.
35.2.1
SAB address map
The Service Access Bus (SAB) gives the user access to the internal address space and other
features through a 36 bits address space. The 4 MSBs identify the slave number, while the 32
LSBs are decoded within the slave’s address space. The SAB slaves are shown in
35.2.2
SAB security restrictions
The Service Access bus can be restricted by internal security measures. A short description of
the security measures are found in the table below.
Table 35-1.
SAB Slaves, addresses and descriptions.
Slave
Address [35:32]
Description
Unallocated
0x0
Intentionally unallocated
OCD
0x1
OCD registers
HSB
0x4
HSB memory space, as seen by the CPU
HSB
0x5
Alternative mapping for HSB space, for compatibility with
other 32-bit AVR devices.
Memory Service
Unit
0x6
Memory Service Unit registers
Reserved
Other
Unused
Summary of Contents for AT32UC3A3128
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