Datasheet
748
AT32UC3A
Memory can be written while the CPU is executing, which can be utilized for debug purposes.
When downloading a new program, the JTAG HALT instruction should be used to freeze the
CPU, to prevent partially downloaded code from being executed.
36.7 JTAG Instruction Summary
The implemented JTAG instructions in the AVR32 are shown in the table below.
36.7.1 Security restrictions
When the security fuse in the Flash is programmed, the following JTAG instructions are
restricted:
• NEXUS_ACCESS
• MEMORY_WORD_ACCESS
• MEMORY_BLOCK_ACCESS
• MEMORY_SIZED_ACCESS
Table 36-2. JTAG Instruction Summary
Instruction
OPCODE Instruction Description Page
0x01 IDCODE Select the 32-bit ID register as data register. 749
0x02 SAMPLE_PRELOAD
Take a snapshot of external pin values without affecting system
operation.
749
0x03 EXTEST
Select boundary scan chain as data register for testing circuitry
external to the device.
749
0x04 INTEST Select boundary scan chain for internal testing of the device. 749
0x06 CLAMP
Bypass device through Bypass register, while driving outputs from
boundary scan register.
750
0x0C AVR_RESET Apply or remove a static reset to the device 757
0x0F CHIP_ERASE Erase the device 757
0x10 NEXUS_ACCESS
Select the SAB Address and Data registers as data register for the
TAP. The registers are accessed in Nexus mode.
751
0x11 MEMORY_WORD_ACCESS
Select the SAB Address and Data registers as data register for the
TAP.
754
0x12 MEMORY_BLOCK_ACCESS
Select the SAB Data register as data register for the TAP. The
address is auto-incremented.
755
0x13 CANCEL_ACCESS Cancel an ongoing Nexus or Memory access. 756
0x14 MEMORY_SERVICE
Select the SAB Address and Data registers as data register for the
TAP. The registers are accessed in Memory Service mode.
752
0x15 MEMORY_SIZED_ACCESS
Select the SAB Address and Data registers as data register for the
TAP.
753
0x17 SYNC Synchronization counter 757
0x1C HALT Halt the CPU for safe programming. 758
0x1F BYPASS Bypass this device through the bypass register. 750
Others N/A Acts as BYPASS
32058K
AVR32-01/12