recently, I have encountered the same problem with the DSPI POP Register as Rehan Kehan .The original question issued by Rehan Kehan before, so i quote the detail of the problem as following:
We are using DSPI 0 of MPC5645S device. We have configured the module as RXFIFO disable. Following are our configuration.
DSPI_0.MCR.B.DIS_RXF = 1;
DSPI_0.MCR.B.ROOE = 1;
DSPI_0.RSER.B.RFDF_RE = 0x1; //enable Rx interrupt
DSPI_0.RSER.B.TCF_RE = 0x1; //enable Tx interrupt
DSPI_0.MCR.B.HALT=0; //start the transfers.
This is my ISR
DSPI_0.RSER.B.RFDF_RE = 0;
receive_dspi_data0 = (uint16_t) DSPI_0.POPR.R;
DSPI_0.SR.R = DSPI_0.SR.R | 0x80020000;
receive_flag0 = 1;
DSPI_0.RSER.B.RFDF_RE = 1;
The problem is whenever ISR gets triggered. The data in variable receive_dspi_data0 read as zero every time even if the POP register value in debugger window shows valid data. What I have found is, this peripherals are memory mapped registers and the DSPI_0.POP is mapped to address 0xfff90038, when I look into memory window the value at this address is zero, but in debugger window it is valid data. what I observed is it takes time to see the valid data at 0xfff90038. but I cannot read the data by using DSPI_0.POPR.R in one time. That's why I am always getting zero value.
In reference manual it is written that
For compatibility, configure the TLB (MMU table) entry for DSPIx_POPR as guarded.
What does it mean. how to make DSPI_0.POP value to be read in one ISR cycle. what I can do so that value at address 0xfff90038 becomes valid data as soon program enters the receive ISR.
the answer to this problem seems didn't work，so i wonder if there is some configurations i missed, pls help！