Motorola DSP56009 User Manual page 125

The memory read transfer starts only if the EDRB is empty. Data formed in the EDRB
is transferred to the EDRR only if the EDRR is empty. This feature ensures
synchronization between DSP reads of data and memory reads, even if the DSP is not
emptying the EDRR in real time, as can happen while debugging via the OnCE port.
The EBARx can optionally be post-incremented by one after each read transfer. In
this case, the incremented value will be available in the EBARx at the end of the first
executed instruction after all memory read accesses have occurred for this particular
memory-read transfer.
Example 4-2 Successive Memory-Read Transfers with ERTS = 0
The following procedure describes a sequence of successive memory-read
transfers with ERTS = 0. This procedure utilizes the pipeline property for better
performance.
movep #RAM,X:<<ECSR
movep #BAR0,X:<<EBAR0
movep #OFF_1,X:<<EOR0
movep #OFF_2,X:<<EOR0
-
-
-
movep X:<<EDRR0,X0
movep #OFF_3,X:<<EOR0
-
-
-
movep X:<<EDRR0,X0
movep #OFF_4,X:<<EOR0
-
-
-
movep X:<<EDRR0,X0
-
-
-
movep X:<<EDRR0,X0
MOTOROLA
; define memory access mode
; define base address
; trigger first memory read transfer
; (using EBAR0)
; initiate the second read transfer
; (pipelined)
; this will be pending until the
; previous transfer terminates
; perform other operations
; or poll EDRF for EDRR full
; or wait a sufficient number of Icyc
; and then,
; read the data delayed by OFF_1
; initiate the next memory read transfer
; perform other operations
; or poll EDRF for EDRR full
; or wait a sufficient number of Icyc
; and then,
; read the data delayed by OFF_2
; initiate the next memory read transfer
; perform other operations
; or poll EDRF for EDRR full
; or wait a sufficient number of Icyc
; and then,
; read the data delayed by OFF_3
; perform other operations
; or poll EDRF for EDRR full
; or wait a sufficient number of Icyc
; and then,
; read the data delayed by OFF_4
DSP56009 User's Manual
External Memory Interface
EMI Operating Considerations
4-41