How to independently access EMIF_DATA[3] pin for making a wave form

Alex George

Hi There!

I am new to TMS570 micro controllers, and I am in a need of making a waveform (PWM) on EMIF_DATA[3] pin. It will be great if any of you can share your knowledge.

Thanks in advance!

Alex

over 9 years ago

0 Charles Tsai over 9 years ago

TI__Guru**** 191296 points

Hi Alex,
Depending on the device you use, there are other modules (i.e. NHET and ePWM) in the MCU that can generate PWM with your desired frequency and duty cycle. Is there a specific reason to use EMIF_DATA[3]? Normally, the EMIF is used to interface with external memories.

0 Alex George over 9 years ago in reply to Charles Tsai

Prodigy 40 points

Hi Charles,
Yes, we have a specific reason to use EMIF other than NHET.

Thanks
Alex

0 Anthony F. Seely over 9 years ago in reply to Alex George

TI__Guru 68920 points

So Alex, it can't be done. The EMIF data bus is a parallel bus - it's not bit addressable.
The only way to wiggle a single pin is by GPIO control. Many of our peripherals have SET/CLEAR registers where you can write a '1' to a single bit in the SET register and that pin will go high leaving the others unchanged, and a '1' to the CLEAR register will make the pin go low leaving the others unchanged. But that doesn't exist for the EMIF.

0 Charles Tsai over 9 years ago in reply to Anthony F. Seely

TI__Guru**** 191296 points

Alex,
Also suppose you write something to stimulate the EMIF_DATA the data can be in unknown state until it is finally settled.

0 Joe Josn over 9 years ago in reply to Charles Tsai

Intellectual 680 points

Alex, you can latch the state of D[3] with proper latch enable logic (an address decoder, or just cs in select strobe mode?), flip the data bit and write to that address whenever you want to change the state - an expensive pwm! :-)

0 Alex George over 9 years ago in reply to Joe Josn

Prodigy 40 points

Thanks Joe for this suggestions, it was already setup a latch up logic in the Hardware which am using by our Hardware folks. Basically this is a POC kind of work. Now what I am looking for is a timer interrupt, other than RTIs, to write the data onto the EMIF pins in the required time period. Do you have any suggestions?

Thanks
Alex

0 Joe Josn over 9 years ago in reply to Alex George

Intellectual 680 points

Alex,

Use N2HET. You can probably create/manipulate the pwm (bit pattern) you need to update D[3] using HTU periodically without cpu involvement. Why D3 when you could have used any one of the HET pins pwm easy?

Using HET you can generate periodic interrupts or dma requests.

OR use ePWMs if the device has one.

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How to independently access EMIF_DATA[3] pin for making a wave form