Addressing With DAGs
5-6
ADSP-BF535 Blackfin Processor Hardware Reference
Addressing Circular Buffers
The DAGs support addressing circular buffers—a range of addresses con-
taining data that the DAG steps through repeatedly, wrapping around to
repeat stepping through the same range of addresses in a circular pattern.
The DAGs use four types of DAG registers for addressing circular buffers.
For circular buffering, the registers operate this way:
• The Index (I) register contains the value that the DAG outputs on
the address bus.
• The Modify (M) register contains the post-modify amount (posi-
tive or negative) that the DAG adds to the I-register at the end of
each memory access.
• Any M-register can be used with any I-register. The modify value
can also be an immediate value instead of an M-register. The size of
the modify value must be less than or equal to the length (L-regis-
ter) of the circular buffer.
• The Length (L) register sets the size of the circular buffer and the
address range through which the DAG circulates the I-register.
• L is positive and cannot have a value greater than 2
31
– 1. If an
L-register’s value is zero, its circular buffer operation is disabled.
• The Base (B) register or the B-register plus the L-register is the
value with which the DAG compares the modified I-register value
after each access.
To address a circular buffer, the DAG steps the index pointer (I-register)
through the buffer values, post-modifying and updating the index on each
access with a positive or negative modify value from the M-register.
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...