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4.2.1
EMI Base Address Registers (EBAR0 and EBAR1)
The read/write 24-bit EMI Base Address Registers (EBAR0 and EBAR1) contain the
base address used by the EMI to calculate the address (in external memory) of the
word to be accessed. During a read access, the word address is formed by subtracting
the value in the EOR from the value in either EBAR0 or EBAR1 (EBARx). During a
write access, the word address is formed by subtracting the contents of the Write
Offset Register (EWOR) from the contents of EBARx. The EBARx contents can be
incremented after the memory access. The increment operates on all 24 bits of
EBARx. The base address is stored in 24-bit unsigned integer format.
4.2.2
EMI Write Offset Register (EWOR)
The read/write 24-bit EMI Write Offset Register (EWOR) is used by the EMI to
calculate the address (in external memory) of the word to be accessed during write
operations. The address is formed by subtracting the contents of the EWOR from the
contents of EBARx. The offset is stored in 24-bit unsigned integer format. The EWOR
contains a displacement value (from the start of the data-delay buffer) and is used to
access a delayed data sample location. For example, assuming that EBARx points to
the sample at time 0, then in order to write the data sample delayed by N, the value
of N should be written into the EWOR.
Note: The EWOR is cleared by hardware reset and software reset.
MOTOROLA
DSP56009 User's Manual
External Memory Interface
EMI Programming Model
4-7
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