EtherCAT数据帧结构介绍

总报文

参照电子科技大学，蒲婉玲的学位论文“EtherCAT 主站与从站设计与实现”，Ether CAT 通信帧结构采用标准以外网帧结构，是通过对传统协议进行修改形成，在标准协议里插入专用帧类型的 Ether CAT 数据帧，也就是说，标准协议的数据内容就是 Ether CAT 的数据帧。专用帧类型用 0x88A4 进行标记。也因为如此，Ether CAT 通信可被标准的以太网通信完全兼容。
报文数据结构

子报文

子报文包含命令、索引、地址区长度、标志位、状态位、数据区和工作计数器等 7 个部分。报文中的命令一般是 8 位，用来表示报文寻址方式和读写操作；索引就是帧编码；从站通信地址是地址去中的 32 位二进制码；标志位 M 是后续报文的表示，如果 Ether CAT 数据帧有多个子报文，除最后一个子报文的标志位外，其他子报文的标志位都需要被职位；子报文数据属于用户自定义部分，长度一般是 1486 个 byte。

SOEM报文结构介绍

soem文件包中的ethercatmain.h文件中，定义了ecx_context报文数据帧结构和ec_slave子报文数据结构，下面将分别对其进行介绍。

总报文ecx_context

/** Context structure , referenced by all ecx functions*/
struct ecx_context
{
   /** port reference, may include red_port */
   ecx_portt      *port;
   /** slavelist reference */
   ec_slavet      *slavelist;
   /** number of slaves found in configuration */
   int            *slavecount;
   /** maximum number of slaves allowed in slavelist */
   int            maxslave;
   /** grouplist reference */
   ec_groupt      *grouplist;
   /** maximum number of groups allowed in grouplist */
   int            maxgroup;
   /** internal, reference to eeprom cache buffer */
   uint8          *esibuf;
   /** internal, reference to eeprom cache map */
   uint32         *esimap;
   /** internal, current slave for eeprom cache */
   uint16         esislave;
   /** internal, reference to error list */
   ec_eringt      *elist;
   /** internal, reference to processdata stack buffer info */
   ec_idxstackT   *idxstack;
   /** reference to ecaterror state */
   boolean        *ecaterror;
   /** reference to last DC time from slaves */
   int64          *DCtime;
   /** internal, SM buffer */
   ec_SMcommtypet *SMcommtype;
   /** internal, PDO assign list */
   ec_PDOassignt  *PDOassign;
   /** internal, PDO description list */
   ec_PDOdesct    *PDOdesc;
   /** internal, SM list from eeprom */
   ec_eepromSMt   *eepSM;
   /** internal, FMMU list from eeprom */
   ec_eepromFMMUt *eepFMMU;
   /** registered FoE hook */
   int            (*FOEhook)(uint16 slave, int packetnumber, int datasize);
   /** registered EoE hook */
   int            (*EOEhook)(ecx_contextt * context, uint16 slave, void * eoembx);
   /** flag to control legacy automatic state change or manual state change */
   int            manualstatechange;
};

需要特别注意

• 1 从站个数int *slavecount;
• 2 从站列表 ec_slavet *slavelist;

子报文ec_slave

/** for list of ethercat slaves detected */
typedef struct ec_slave
{
   /** state of slave */
   uint16           state;
   /** AL status code */
   uint16           ALstatuscode;
   /** Configured address */
   uint16           configadr;
   /** Alias address */
   uint16           aliasadr;
   /** Manufacturer from EEprom */
   uint32           eep_man;
   /** ID from EEprom */
   uint32           eep_id;
   /** revision from EEprom */
   uint32           eep_rev;
   /** Interface type */
   uint16           Itype;
   /** Device type */
   uint16           Dtype;
   /** output bits */
   uint16           Obits;
   /** output bytes, if Obits < 8 then Obytes = 0 */
   uint32           Obytes;
   /** output pointer in IOmap buffer */
   uint8            *outputs;
   /** startbit in first output byte */
   uint8            Ostartbit;
   /** input bits */
   uint16           Ibits;
   /** input bytes, if Ibits < 8 then Ibytes = 0 */
   uint32           Ibytes;
   /** input pointer in IOmap buffer */
   uint8            *inputs;
   /** startbit in first input byte */
   uint8            Istartbit;
   /** SM structure */
   ec_smt           SM[EC_MAXSM];
   /** SM type 0=unused 1=MbxWr 2=MbxRd 3=Outputs 4=Inputs */
   uint8            SMtype[EC_MAXSM];
   /** FMMU structure */
   ec_fmmut         FMMU[EC_MAXFMMU];
   /** FMMU0 function */
   uint8            FMMU0func;
   /** FMMU1 function */
   uint8            FMMU1func;
   /** FMMU2 function */
   uint8            FMMU2func;
   /** FMMU3 function */
   uint8            FMMU3func;
   /** length of write mailbox in bytes, if no mailbox then 0 */
   uint16           mbx_l;
   /** mailbox write offset */
   uint16           mbx_wo;
   /** length of read mailbox in bytes */
   uint16           mbx_rl;
   /** mailbox read offset */
   uint16           mbx_ro;
   /** mailbox supported protocols */
   uint16           mbx_proto;
   /** Counter value of mailbox link layer protocol 1..7 */
   uint8            mbx_cnt;
   /** has DC capability */
   boolean          hasdc;
   /** Physical type; Ebus, EtherNet combinations */
   uint8            ptype;
   /** topology: 1 to 3 links */
   uint8            topology;
   /** active ports bitmap : ....3210 , set if respective port is active **/
   uint8            activeports;
   /** consumed ports bitmap : ....3210, used for internal delay measurement **/
   uint8            consumedports;
   /** slave number for parent, 0=master */
   uint16           parent;
   /** port number on parent this slave is connected to **/
   uint8            parentport;
   /** port number on this slave the parent is connected to **/
   uint8            entryport;
   /** DC receivetimes on port A */
   int32            DCrtA;
   /** DC receivetimes on port B */
   int32            DCrtB;
   /** DC receivetimes on port C */
   int32            DCrtC;
   /** DC receivetimes on port D */
   int32            DCrtD;
   /** propagation delay */
   int32            pdelay;
   /** next DC slave */
   uint16           DCnext;
   /** previous DC slave */
   uint16           DCprevious;
   /** DC cycle time in ns */
   int32            DCcycle;
   /** DC shift from clock modulus boundary */
   int32            DCshift;
   /** DC sync activation, 0=off, 1=on */
   uint8            DCactive;
   /** link to config table */
   uint16           configindex;
   /** link to SII config */
   uint16           SIIindex;
   /** 1 = 8 bytes per read, 0 = 4 bytes per read */
   uint8            eep_8byte;
   /** 0 = eeprom to master , 1 = eeprom to PDI */
   uint8            eep_pdi;
   /** CoE details */
   uint8            CoEdetails;
   /** FoE details */
   uint8            FoEdetails;
   /** EoE details */
   uint8            EoEdetails;
   /** SoE details */
   uint8            SoEdetails;
   /** E-bus current */
   int16            Ebuscurrent;
   /** if >0 block use of LRW in processdata */
   uint8            blockLRW;
   /** group */
   uint8            group;
   /** first unused FMMU */
   uint8            FMMUunused;
   /** Boolean for tracking whether the slave is (not) responding, not used/set by the SOEM library */
   boolean          islost;
   /** registered configuration function PO->SO, (DEPRECATED)*/
   int              (*PO2SOconfig)(uint16 slave);
   /** registered configuration function PO->SO */
   int              (*PO2SOconfigx)(ecx_contextt * context, uint16 slave);
   /** readable name */
   char             name[EC_MAXNAME + 1];
} ec_slavet;

其中需要特别关注的是

• 1 从站id /** ID from EEprom */ uint32 eep_id;
• 2 输出指针/** output pointer in IOmap buffer */ uint8 *outputs;
• 3 输入指针/** input pointer in IOmap buffer */ uint8 *inputs;

ec_group数据结构

/** for list of ethercat slave groups */
typedef struct ec_group
{
   /** logical start address for this group */
   uint32           logstartaddr;
   /** output bytes, if Obits < 8 then Obytes = 0 */
   uint32           Obytes;
   /** output pointer in IOmap buffer */
   uint8            *outputs;
   /** input bytes, if Ibits < 8 then Ibytes = 0 */
   uint32           Ibytes;
   /** input pointer in IOmap buffer */
   uint8            *inputs;
   /** has DC capabillity */
   boolean          hasdc;
   /** next DC slave */
   uint16           DCnext;
   /** E-bus current */
   int16            Ebuscurrent;
   /** if >0 block use of LRW in processdata */
   uint8            blockLRW;
   /** IO segments used */
   uint16           nsegments;
   /** 1st input segment */
   uint16           Isegment;
   /** Offset in input segment */
   uint16           Ioffset;
   /** Expected workcounter outputs */
   uint16           outputsWKC;
   /** Expected workcounter inputs */
   uint16           inputsWKC;
   /** check slave states */
   boolean          docheckstate;
   /** IO segmentation list. Datagrams must not break SM in two. */
   uint32           IOsegment[EC_MAXIOSEGMENTS];
} ec_groupt;