TMS570LC4357-SEP: EMIF bus access - EMIF is Byte Addressable ?

Amit Jagtap

Part Number: TMS570LC4357-SEP

Tool/software:

Hi,

If my understanding is correct, TMS570 Microcontroller internal memory Flash and SRAM are byte addressable.

The EMIF interface with 22 Address lines can access 4M depth of Memory, an external memory can be 8 bit or 16 bit wide (selected in ASIZE of CEnCFG register).

Irrespective of an external memory being 8 or 16 bits, user can access 4M addess locations. Kindly clarify this point.

Secondly As per TRM, 16MB is the actual memory range addressable for each chip select, but since there are only 22 address lines, additional GPIOs to be used as higher address lines. Kindly clarify.

Also, please clarify whether addressable range is 16MB or 16M locations (8 or 16 bit wide memory), as in reference manual it is written as 16 MB. which may contradict to in case of 16 bit Async Memory with same address locations

Finaly, pls clarify whether EMIF bus access is byte addressable?

Regards,

Amit

4 months ago

0 jagadish gundavarapu 4 months ago

TI__Guru 70241 points

Hi Amit,

Amit Jagtap said:
Secondly As per TRM, 16MB is the actual memory range addressable for each chip select, but since there are only 22 address lines, additional GPIOs to be used as higher address lines. Kindly clarify.

The TRM is correct, we can access upto 16MB memory using the EMIF.

Let me explain with an example:

If you are interfacing 8-bit asynchronous memory, then the least significant address lines (A0 and A1) of the external memory will be connected to Byte Address lines (BA0 and BA1) like as shown below:

So that means the max address line A21 of the controller will be connected with A23 of the external memory that means the total addressable memory range will now become 2^24 * 8bits, which is nothing but 16MB.

Similarly, if we connect 16-bit memory with the device:

then the least significant address lines (A0) of the external memory will be connected to Byte Address lines (BA1) like as shown below:

So that means the max address line A21 of the controller will be connected with A22 of the external memory that means the total addressable memory range will now become 2^23 * 16bits, which is nothing but 16MB.

For more details, please refer below thread once:

(10) TMS570LC4357-EP: Address Lines EMIF Bus connection for External Memory - Arm-based microcontrollers forum - Arm-based microcontrollers - TI E2E support forums

Amit Jagtap said:
Finaly, pls clarify whether EMIF bus access is byte addressable?

Yes you can do byte addressing using EMIF.

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Thanks & regards,
Jagadish.