Why timer's value channel 1 can't big than channel 0?

Question

Hi: 
 
 I using timer0's channel_0, channel_1 to drive a ADC, a handle_function. 
 unfortunately, I discover my timer with channel_1 didn't work when channel_1' value bigger than channel_0. 
 How should I do?

//=========================================================================
// ADC functions (timer 0, channel_0)
//=========================================================================
void saadc_sampling_event_init(void) {
 ret_code_t err_code;

 err_code = nrf_drv_ppi_init();
 APP_ERROR_CHECK(err_code);

 uint32_t timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&m_timer,
 NRF_TIMER_CC_CHANNEL0);
 uint32_t saadc_sample_task_addr = nrf_drv_saadc_sample_task_get();

 /* setup ppi channel so that timer compare event is triggering sample task in SAADC */
 err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
 APP_ERROR_CHECK(err_code);

 err_code = nrf_drv_ppi_channel_assign(m_ppi_channel,
 timer_compare_event_addr,
 saadc_sample_task_addr);
 APP_ERROR_CHECK(err_code);
}


void saadc_sampling_event_enable(void) {
 ret_code_t err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);

 APP_ERROR_CHECK(err_code);
}


void saadc_callback(nrf_drv_saadc_evt_t const * p_event) {
 if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
 {
 ret_code_t err_code;

 err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
 APP_ERROR_CHECK(err_code);
 v_usb_i = p_event->data.done.p_buffer[0];
 v_usb_f = coe_of_v_usb * (double)v_usb_i;
 }
}


void saadc_init(void) {
 ret_code_t err_code;
 nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE_G(NRF_SAADC_INPUT_AIN7);
 
 err_code = nrf_drv_saadc_init(NULL, saadc_callback);
 APP_ERROR_CHECK(err_code);
 
 nrf_saadc_resolution_set(NRF_SAADC_RESOLUTION_12BIT);

 err_code = nrf_drv_saadc_channel_init(0, &channel_config);
 APP_ERROR_CHECK(err_code);

 err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0], SAMPLES_IN_BUFFER);
 APP_ERROR_CHECK(err_code);

 err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1], SAMPLES_IN_BUFFER);
 APP_ERROR_CHECK(err_code);

}

//=========================================================================
// timer handler
//=========================================================================
void my_timer_handler(nrf_timer_event_t event_type, void* p_context) {
 if ( event_type == NRF_TIMER_EVENT_COMPARE0 ) {
 
 } else if ( event_type == NRF_TIMER_EVENT_COMPARE1 ) {
 
 nrf_gpio_pin_toggle(LED0_pin);
 }
}

//=========================================================================
// init function
//=========================================================================
const nrf_drv_timer_t MY_TIMER_0 = NRF_DRV_TIMER_INSTANCE(0);
void Init() {
 //
 saadc_init();
 saadc_sampling_event_init();
 saadc_sampling_event_enable();

 nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
 nrf_drv_timer_init(&MY_TIMER_0, &timer_cfg, &my_timer_handler);
 nrf_drv_timer_extended_compare(&MY_TIMER_0,
 NRF_TIMER_CC_CHANNEL0,
 nrf_drv_timer_ms_to_ticks(&MY_TIMER_0, 50),
 NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
 true);
 nrf_drv_timer_extended_compare(&MY_TIMER_0,
 NRF_TIMER_CC_CHANNEL1,
 nrf_drv_timer_ms_to_ticks(&MY_TIMER_0, 100), // Channel_1 100ms
 NRF_TIMER_SHORT_COMPARE1_CLEAR_MASK,
 true);
 nrf_drv_timer_enable(&MY_TIMER_0);
}