EcRT of EtherCAT igh source code_ slave_ config_ Understanding of dc() function.

To sum up my understanding of igh Of ecrt_slave_config_dc（） The understanding of function . Refer to the igh Of example Inside “dc_user routine ”.
There is such a code in the routine ：

// configure SYNC signals for this slave
	ecrt_slave_config_dc(sc, 0x0700, PERIOD_NS, 4400000, 0, 0);

stay slave_config.c The function definition can be found in the file ：

/** Configure distributed clocks. * * Sets the AssignActivate word and the cycle and shift times for the sync * signals. * * The AssignActivate word is vendor-specific and can be taken from the XML * device description file (Device -> Dc -> AssignActivate). Set this to zero, * if the slave shall be operated without distributed clocks (default). * * This method has to be called in non-realtime context before * ecrt_master_activate(). * * \attention The \a sync1_shift time is ignored. */
void ecrt_slave_config_dc(
        ec_slave_config_t *sc, /**< Slave configuration. */
        uint16_t assign_activate, /**< AssignActivate word. */
        uint32_t sync0_cycle, /**< SYNC0 cycle time [ns]. */
        int32_t sync0_shift, /**< SYNC0 shift time [ns]. */
        uint32_t sync1_cycle, /**< SYNC1 cycle time [ns]. */
        int32_t sync1_shift /**< SYNC1 shift time [ns]. */
        );
void ecrt_slave_config_dc(ec_slave_config_t *sc, uint16_t assign_activate,
        uint32_t sync0_cycle_time, int32_t sync0_shift_time,
        uint32_t sync1_cycle_time, int32_t sync1_shift_time)
{
    
    ec_ioctl_config_t data;
    int ret;

    data.config_index = sc->index;
    data.dc_assign_activate = assign_activate;
    data.dc_sync[0].cycle_time = sync0_cycle_time;
    data.dc_sync[0].shift_time = sync0_shift_time;
    data.dc_sync[1].cycle_time = sync1_cycle_time;
    data.dc_sync[1].shift_time = sync1_shift_time;

    ret = ioctl(sc->master->fd, EC_IOCTL_SC_DC, &data);
    if (EC_IOCTL_IS_ERROR(ret)) {
    
        fprintf(stderr, "Failed to set DC parameters: %s\n",
                strerror(EC_IOCTL_ERRNO(ret)));
    }
}

1. First of all, let's talk about assign_activate Variables are 0x0700

according to igh The explanation given ,assign_activate The value of the variable can be in the slave station xml Found in the file ：

Open one xml file , The relevant parameters can be found according to the prompts ：

But here is 0x0300, instead of 0x0700. I have verified , Most slave stations xml Of AssignActivate The value is 0x0300.
What is the relationship between these two values ？ Why is it set like this ？
The next section is my reasoning analysis with a little friend , It could be wrong , Please correct ！！！

2. analysis 0x0700 and 0x0300

In this section, I refer to this elder brother's article https://blog.csdn.net/ethercat_i7/article/details/77890740, I benefited a lot .

igh/ethercat-hg/master/fsm_slave_config.c
/** Slave configuration state: DC START. */
void ec_fsm_slave_config_state_dc_start(
        ec_fsm_slave_config_t *fsm /**< slave state machine */
        )
{
    
    ec_datagram_t *datagram = fsm->datagram;
    ec_slave_t *slave = fsm->slave;
    ec_slave_config_t *config = slave->config;

	......

    EC_SLAVE_DBG(slave, 1, "Setting DC AssignActivate to 0x%04x.\n",
            config->dc_assign_activate);

    // assign sync unit to EtherCAT or PDI
    ec_datagram_fpwr(datagram, slave->station_address, 0x0980, 2);
    EC_WRITE_U16(datagram->data, config->dc_assign_activate);
    fsm->retries = EC_FSM_RETRIES;
    fsm->state = ec_fsm_slave_config_state_dc_assign;
}

The code here finds AssignActivate And 0x0980 Linked together , and 0x0980 It is DC Control related registers , see lan9252 perhaps ET1100 You can find the relevant settings in the data book of the chip . Recommend here 《 Industrial Ethernet fieldbus EtherCAT Driver design and application 》 This blue book , A new version has just been released this year . There is also an explanation of relevant registers in the book . The following figure shows the contents of the book .

0x0981 and 0x0980 The two registers add up to 16 position .0x0981 Take up high 8 position ,0x0980 Low occupancy 8 position .0x0700 and 0x0300 That is, the setting of these two registers .

Refer to the register manual ：
0x0981 Of 0、1 Location 1、 Other locations 0 It indicates that the “ Activate the operating cycle , Activate SYNC0”, namely 0x0300;
0x0981 Of 0、1、2 Location 1、 Other locations 0 It indicates that the “ Activate the operating cycle , Activate SYNC0, Activate SYNC1”, namely 0x0700;

3.ecrt_slave_config_dc（） After 4 Parameters

sync0_cycle_time, sync0_shift_time, sync1_cycle_time, sync1_shift_time this 4 The parameters are set separately SYNC0、1 Period and offset of .
Recommended reference 《EtherCAT_Communication_EN-》 and 《 Industrial Ethernet fieldbus EtherCAT Driver design and application 》.

DC I still don't understand a lot about the relevant content , After that, through continuous learning 、 practice 、 Ask the big man , To improve your cognition .

reference
【1】https://blog.csdn.net/ethercat_i7/article/details/77890740
【2】https://blog.csdn.net/GW569453350game/article/details/51612802
【3】http://lists.etherlab.org/pipermail/etherlab-users/2016/003013.html
【4】https://blog.csdn.net/PI_sunyang/article/details/95601486
【5】《EtherCAT_Communication_EN-》
【6】《 Industrial Ethernet fieldbus EtherCAT Driver design and application 》