Motorola DSP96002 用户手册

 

One or more of the DSP96002 memory sources (X data memory, Y data memory and  program memory)

may be accessed during the execution of an instruction.  Each of these memory sources may be internal or

external to the DSP96002.  Three address buses (XAB, YAB and PAB) and four data buses (XDB, YDB,

PDB  and GDB) are available for internal memory core (as opposed to DMA)  accesses during one  instruc-

tion cycle.  

The DSP96002 has two external expansion ports (Port A and Port B), that  function as extensions of the

internal address and data buses for  external memory accesses.  If all memory sources are internal to the

DSP96002, one or more of the three memory sources may be accessed in one  instruction cycle (i.e., pro-

gram memory access or program memory access  plus an X, Y, XY or L memory reference; refer  to Section

5.6 for a description of operand  references).  However, when one or more of the memories are external to

the DSP96002, and the external memories are located in the same expansion  port, memory references

may require additional instruction cycles.  

If, in one instruction cycle, more than one external access is  required on the same port, the accesses will

be made with the following  priority:  

1. 

X memory.  

2. 

Y memory.  

3. 

Program memory.  

4. DMA.