Does the "EasyDMA MAXCNT bit length" in i2s means RXTXD.MAXCNT(size of RXD and TXD buffers) ?

[swna3708]

Dear All.

I have question about some hardware specifications.

below is i found in nordic info.

and it says I2s have 0, 14, 14(52810, 52832, 52840) of Easy DMA MAXCNT length.

I understood that means that The '14' is the size of rxd and txd buffers in Easy DMA.

am i correct? if not, how i understand that specification?? 

 

thanks.

best regard.

[Einar Thorsrud]

Hi,

These numbers are the bit size of the MAXCNT register, which then gives you the maximum buffer length. But note that it is bit lengths. So if the MAXCNT is 14 bits, this means that the maximum buffer size is 2^14 bytes = 16384 bytes.

[swna3708]

thank you Einar! 

now i'm clearly understand! thank you!

[Hugh.G.Yeom]

Hi, I sutudy about I2S in NRF52840. Just i confused about size... 

In doucument : https://infocenter.nordicsemi.com/topic/ps_nrf52840/i2s.html?cp=4_0_0_5_10_6#concept_gq4_jly_vr

I think one Buffer in Memory is 32bit. so Is maximum size of memory is not 2^14^x32 bit (2^132x2 Bytes = 32,768)?

And can I ask if I wanna send whole array,

I2S->RXTXD.MAXCNT = 16384,
16bit PCM data MONO,
data_array[16384] = {data};

Is the maximum number of bytes that can be transferred 16384 bytes?

or 

I2S->RXTXD.MAXCNT = 8192
16bit PCM data MONO,
data_array[16384] = {data};

is correct?

[Einar Thorsrud]

All sizes are in bytes (in other works, the size of a 32 bit register is 4). So with a MAXCNT (length) register of 14 bits, the maximum is 16384 bytes.

[Hugh.G.Yeom]

Thanks a lot!