AT32UC3A3256S_2 Datasheet, PDF (957/1014 Pages) ATMEL Corporation – 32-bit AVR®Microcontroller

AT32UC3A3/A4
34.5.3.6
34.5.3.7
Table 34-21. MEMORY_BLOCK_ACCESS Details (Continued)
Instructions
Details
DR input value (Data write phase)
dddddddd dddddddd dddddddd dddddddd xx
DR output value (Data read phase) eb dddddddd dddddddd dddddddd dddddddd
DR output value (Data write phase) xx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxeb
The overhead using block word access is 4 cycles per 32 bits of data, resulting in an 88% trans-
fer efficiency, or 2.1 MBytes per second with a 20 MHz TCK frequency.
CANCEL_ACCESS
If a very slow memory location is accessed during a SAB memory access, it could take a very
long time until the busy bit is cleared, and the SAB becomes ready for the next operation. The
CANCEL_ACCESS instruction provides a possibility to abort an ongoing transfer and report a
timeout to the JTAG master.
When the CANCEL_ACCESS instruction is selected, the current access will be terminated as
soon as possible. There are no guarantees about how long this will take, as the hardware may
not always be able to cancel the access immediately. The SAB is ready to respond to a new
command when the busy bit clears.
Starting in Run-Test/Idle, CANCEL_ACCESS is accessed in the following way:
1. Select the IR Scan path.
2. In Capture-IR: The IR output value is latched into the shift register.
3. In Shift-IR: The instruction register is shifted by the TCK input.
4. Return to Run-Test/Idle.
Table 34-22. CANCEL_ACCESS Details
Instructions
Details
IR input value
10011 (0x13)
IR output value
peb01
DR Size
1
DR input value
x
DR output value
0
SYNC
This instruction allows external debuggers and testers to measure the ratio between the external
JTAG clock and the internal system clock. The SYNC data register is a 16-bit counter that
counts down to zero using the internal system clock. The busy bit stays high until the counter
reaches zero.
Starting in Run-Test/Idle, SYNC instruction is used in the following way:
1. Select the IR Scan path.
2. In Capture-IR: The IR output value is latched into the shift register.
3. In Shift-IR: The instruction register is shifted by the TCK input.
4. Return to Run-Test/Idle.
5. Select the DR Scan path.
32072C–AVR32–2010/03
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