Some of my PWM signals fed into CPLD chip are MISSING?

--- Quote Start ---

Hello,

I connected my TI DSP TMS320LF2810's PWM signals output pins to the pins in Bank3 of my CPLD chip EPM1270F256.

There are overall 6 PWM signals from DSP to CPLD chip. However, there are only two channels of PWM signals can be seen from DSP output pins to CPLD input pins. The other four channels have no signals at all!

I am pretty much sure that my DSP code is fine, which means that there are definitely 6 PWM outputs. And, I checked all 6 input pins in CPLD chip which are set the same as "Direction - input" and " 3.3V-LVTTL(default)" .

But, why are there only two channels of PWM signals can be output from DSP but the signals in the other four channels are all MISSING?

I do appreciate your help if you could shed some light here...

--- Quote End ---

to make sure you have 6 active dsp outputs connect one known active pwm output to all 6 outputs and check.

Hi Kaz,

Sorry, I don't quite get you. Do you mean that connect all 6 DSP PWM output pins to one known PWM output pin in the DSP?

I am very sure the code is fine since I tried it in another version of my board in which I used the same DSP chip but without CPLD chip. The 6 PWM outputs are active from the DSP.

Thanks!

--- Quote Start ---

Hi Kaz,

Sorry, I don't quite get you. Do you mean that connect all 6 DSP PWM output pins to one known PWM output pin in the DSP?

I am very sure the code is fine since I tried it in another version of my board in which I used the same DSP chip but without CPLD chip. The 6 PWM outputs are active from the DSP.

Thanks!

--- Quote End ---

I suggested driving all 6 dsp output pins by one known pwm signal. But you seem to say that all 6 output pins are active without cpld so something went wrong with cpld connection. How do you observe the pins? could be they are accidentally connected to ground or Vcc

No....those pins are not connected to Vcc or GND. Could be my CPLD chip's pin settings are not correct? Should that be " 3.3V schmitt trigger input", not the "3.3V-LVTTL" input?

I found that if I load no code to CPLD while loading my C code into DSP only, there are no active PWM signals from DSP to CPLD at all although my DSP is running and supposingly there should be PWM signals...