Hello team,
I would like to confirm about the VC5509A EMIF interface.
Would you please answer the following questions?
[Background of the questions]
1. We want to use the VC5509A EMIF as an 8-bit Asynchronous interface.
2. We want to connect 8-bit wide Asynchronous RAM with VC5509A EMIF and transfer data by DMA from DSP internal memory (DARAM or SARAM) to this Asynchronous RAM. In this case, the data type should be 16-bit (short) for DSP and 8-bit for Asynchronous RAM connected with EMIF.
[Question]
Q1. If we want to use the EMIF as an 8-bit asynchronous interface, should we have to use it as a read-only memory?
Or, is it possible to write data to 8-bit Asynchronous memory?
Q2. If it is possible to write 8-bit data with EMIF, please tell us how is the byte order (endian) in the case of sending the data by DMA from DSP (16-bit) to EMIF (8-bit)?
For example, 16-bit data in DSP DARAM or SARAM is like below;
15 8 7 0
|<---Upper8bit--->|<---Lower8bit--->|
If the above data is transferred to external RAM, which byte order is correct?
7 0
|<---Upper 8-bit--->| Address +0
|<---Lower 8-bit--->| Address +1 ... big endian
or
7 0
|<---Upper 8-bit--->| Address +0
|<---Lower 8-bit--->| Address +1 ... little endian
According to the following description, it seems it is possible to read but not possible to write to the 8-bit wide asynchronous RAM. But please let me double check.
TMS320VC5503/5507/5509 DSP External Memory Interface (EMIF) Reference Guide (Spru670a.pdf)
P.1-6
Note: The TMS320VC5503/5507/5509A devices support accesses to 8-bit-wide memory, but the TMS320VC5509 devices do not. On the TMS320VC5503/5507/5509A devices, the only supported 8-bit-wide accesses are reads from asynchronous memory.
There are same descriptions in some other places like P.1-12, P.2-2, P.2-4, P4-7, P.4-13, AppendixB and etc...
Best Regards,
Nobu Arai
