CVI overflow and CVO underflow

Hi,

CVI(run control) -- CVO(run control) ,

cvi always overflow,cvo always underflow. why? How to set the fifo depth?

nios config code is as follows,

/**************************** CTI **************************************/

printf("/*******************************************\n");

printf("CTI_control is %x!\n",CTI->control );

printf("CTI_STATUS is %x!\n",CTI->status );

printf("\n");

//

// updata control data

//

CTI->control = 0x0006;

//

// set go bit 1

//

CTI->control = CTI->control | 0x0001;

printf("After config.\n");

printf("CTI_control is %x!\n",CTI->control );

printf("CTI_STATUS is %x!\n",CTI->status );

printf("\n");

// /************************** ITC ****************************************/

printf("/*******************************************\n");

//

// mode1 HD

// disable mode1_valid

ITC->mode1_valid = 0;

// set mode1 registers

ITC->mode1_control = 1;

ITC->mode1_sample_count = 1920;

ITC->mode1_f0_line_count = 540;

ITC->mode1_f1_line_count = 540;

ITC->mode1_hfront_porch = 0;

ITC->mode1_hsyn_length = 0;

ITC->mode1_h_blanking = 720;

ITC->mode1_vfront_porch = 0;

ITC->mode1_vsync_length = 0;

ITC->mode1_v_blanking = 22;

ITC->mode1_f0_vfront_porch = 0;

ITC->mode1_f0_vsync_length = 0;

ITC->mode1_f0_v_blanking = 23;

ITC->mode1_active_picture_line = 21;

ITC->mode1_f0_v_rising = 561;

ITC->mode1_field_rising = 564;

ITC->mode1_field_falling = 1;

ITC->mode1_std = 0;

// ITC->mode1_sof_sample;

// ITC->mode1_sof_line;

// ITC->mode1_vcoclk_div;

ITC->mode1_ancillary_line = 9;

ITC->mode1_f0_ancillary_line = 571;

// enable mode1_valid

ITC->mode1_valid = 1;

//

// mode2 SD

// disbale mode1_valid

ITC->mode2_valid = 0;

// set mode1 registers

ITC->mode2_control = 3;

ITC->mode2_sample_count = 720;

ITC->mode2_f0_line_count = 288;

ITC->mode2_f1_line_count = 288;

ITC->mode2_hfront_porch = 0;

ITC->mode2_hsyn_length = 0;

ITC->mode2_h_blanking = 144;

ITC->mode2_vfront_porch = 0;

ITC->mode2_vsync_length = 0;

ITC->mode2_v_blanking = 24;

ITC->mode2_f0_vfront_porch = 0;

ITC->mode2_f0_vsync_length = 0;

ITC->mode2_f0_v_blanking = 25;

ITC->mode2_active_picture_line = 23;

ITC->mode2_f0_v_rising = 311;

ITC->mode2_field_rising = 313;

ITC->mode2_field_falling = 1;

ITC->mode2_std = 0;

// ITC->mode2_sof_sample;

// ITC->mode2_sof_line;

// ITC->mode2_vcoclk_div;

ITC->mode2_ancillary_line = 8;

ITC->mode2_f0_ancillary_line = 321;

// enable mode2_valid

ITC->mode2_valid = 1;

printf("ITC control is %x!\n",ITC->control );

printf("ITC status is %x!\n",ITC->status );

// enbale control, cvo output data

ITC->control = 0x1e;

ITC->control = ITC->control | 0x01;