EMIF CE2 space can be read but writing to same space is not working

 Dear Titusrathinaraj Stalin,

I know all these conditions. From the board is powering up AWE pin always shows 2.2V. I want to know why AWE pin always show 2.2V. I can read from the specific location. But writing to the location doesn't have any effect. I checked with CRO, trigger is coming on CRO when writing to EMIF.

Rakesh,

You probably have more than one problem. Is this a new design you have done with the C6211 for a new custom board? If so, why did you choose such an old processor for a new design?

You can check the datasheet for the values of Voh, Ioh, and DVdd, then verify all of them You have said that Voh for AWE is 2.2V which is outside the spec, so you have some problem with Ioh or DVdd.

Why do you need a transceiver between the DSP and Async memory? Until you supply the information Titus requested, we cannot guess at what you have done wrong in the design.

How are you able to confirm you have successfully written to the memory if you are not able to write to it? Are you looking at some of the signals on the scope to confirm this or reading valid data back?

During a write operation, does the AWE never go low at all? Do you see the other signals on the EMIF occurring normally, as shown in the datasheet and EMIF User Guide?

Regards,
RandyP

Randy,

Accoding to TMS320C6211 datasheet, there are 32 data pins. MY custom board with the data pins to B port of the two sn74lvch16245a transceiver ICs with AWE pin as the DIR pin of the transceiver, /OE pin is connected to CE2 signal.

When I am writng to CE2 spaces and /OE pin is logically low and DIR pin also low. so B to A operation takeplace in the transceiver as per its data sheet. How I checked whether writing is successful or not is that i interfaces an LED with one of the pins in the A port of the transceiver.

ie ED0-ED15 of DSP are connected to 1B1 to 2B8 successively and  getting EDT0-ED15 from the A port for first transceiver similarly ED16 - ED31 to the second Transceiver.

For Example:

If I Interfaces an LED on the EDT6, If I want to turn on that LED I have to do only write this:

*(volatile int *) 0xA0000000 = 0x00000040;

I turned on the LED for my project like this, But only when AWE pin is manually grounded. If it so further LEDs cannot be turned on and it is logically and technically wrong also.

I have three questions for you.

1). What will be the status of the AWE pin when board is powering up?

2). Why AWE pin of the my board is showing a sudden stream of high to low transition continously on the CRO with peak as 2.2V and low as 0v ?

3). Is this my board problem because I havn't done any modification to my board rather than taken LEDs from the transceiver ICs?

If you are still confusing i can attach the schematic of my board,

Please help me.........

Rakesh,

You need to solve your 2.2V problem before trying to solve your logic design problem. The voltage problem means there is a board design or fabrication problem, or another logic problem that is causing contention on the AWE signal. This work on your custom board to find the problem, and it is not always easy to do. You may have to lift solder pads or cut traces to find what is happening. Look at other signals to see if any others are also only reaching 2.2V, or especially if any others match the AWE waveform.

You also need to re-examine your logic plan for the SN74LVCH16245A buffer. Your statements and logic design do not match the datasheet.

Rakesh T said:

AWE pin as the DIR pin of the transceiver, /OE pin is connected to CE2 signal.

This means during the Setup and Hold periods of the EMIF write cycle both the DSP and the 16245 will be driving the ED bus. This bus contention may be destructive to the DSP and must be avoided. There is no trivial solution for placing this buffer on the EMIF bus; you will have to use additional logic components to do this correctly. I do not have an answer for you on how to do that.

An LED is not a reliable method for determining if a valid write has occurred. The LED is not a memory element, nor is the 16245, so no logic-level retention can occur. Are you saying that you see the LED blink on, or that you see the LED turn on and stay on?

1) For AWE initial state, please see Figure 31 in the datasheet for the RESET timing. You will see the unknown nature of the EMIF Z signals prior to RESET being applied and during power on.

2) Your oscillation and low voltage on AWE most likely mean there is a board fabrication problem, as I mentioned at the top of this post.

Regards,
RandyP

Hello Rakesh,

If you are intended to use the EMIF interface for asynchronous memory interfacing, could you please elaborate why you are using transceiver in between the SoC and memory device ?

Are you connecting AWE and /OE signals to both tranceivers and memory device ?

Testing the write process with the use of LED is not a right method. Please try to read back the data from the memory device and check.

Rakesh Says said:

I have three questions for you.

1). What will be the status of the AWE pin when board is powering up?

2). Why AWE pin of the my board is showing a sudden stream of high to low transition continously on the CRO with peak as 2.2V and low as 0v ?

3). Is this my board problem because I havn't done any modification to my board rather than taken LEDs from the transceiver ICs?

1. During power on reset, the EMIF signals are tristated. Upon deassertion of power on reset, the EMIF signals are configured as output and driven to inactive state. In case of AWE signal, it will be driven high after power on reset. Please refere figure 31 in TMS320C6211 datasheet.

2. At what time you observe this voltage variation at AWE pin ? What are the levels of other signals during AWE voltage variation ? 2.2V at AWE pin is not considerable for logic high as the voltage level is less than the Voh level. Please check the DVdd in your board.

3. I am not sure about your problem, Please share the schematics to look into detail.

Regards,

Senthil