24-bit / 32-bit UDB Timer DMA Transfer

[shepdog87]

Hello,

I am using a time-stamp method of measuring a frequency of a signal. The signal is a square wave, and causes a DMA transfer to start when a rising edge is detected. There is a circular RAM buffer that holds the timestamps / counts of the timer each time the input signal has a rising edge.  A function is called periodically to subtract the counts from each other to estimate the frequency.

I used the example project from the CONSULTRON which is posted here:

https://community.cypress.com/t5/Code-Examples/Multi-Input-Frequency-Measurement-Tutorial/m-p/183038

Everything works as expected when I use the "Fixed Function" timer block with 16-bits. However, when I try changing it to a 24 or 32-bit UDB timer block, the counts do not make sense. The least-significant-byte of the RAM buffer always has the same value for some reason. When I look at the debug window for the component, the count matches what is expected in the MEMORY viewer, but it seems like the value at that address is not being transferred via DMA? 

I referenced AN61102 which shows how to transfer 32-bit values from 16-bit spokes. I added another DMA channel as an intermediate step, and from the intermediate step goes to the larger buffer.

I was using the following #define in the DMA configuration to retrieve the counts, which is 0x4000_6508: Timer_Count_COUNTER_LSB_PTR_8BIT