TX_FIFO_ALMOST_EMPTY Interrupt Problem

hello,

i work with the IDS014A4 SPIRIT1 WMbus board,

i like to send a frame with the C1 mode(unidirectionel Sent)​.

my first question is : why the Tx frame preparation is limited with12 bytes ?

my programme can not sendall the data only when i replace :

SpiritSpiWriteLinearFifo(12, PhyTxFrame.DataBuff);

with

SpiritSpiWriteLinearFifo(PhyTxFrame.length, PhyTxFrame.DataBuff);

did I make the right change ?

if not what is the proper solution?

if not, my code does not pass by this condition:

       else if (irqStatus.IRQ_TX_FIFO_ALMOST_EMPTY)

Best Regards.