Beckhoff EtherCAT Technology Section I Manual de usuario descargar pdf (Pagina 64)

SyncManager

I-44 Slave Controller – Technology

The content of an EtherCAT mailbox header is shown in Figure 25.

Figure 25: EtherCAT Mailbox Header (for all Types)

Table 24: EtherCAT Mailbox Header

Field

Data Type

Value/Description

Length

WORD

Number of Bytes of this mailbox command excluding the mailbox

header

Address

WORD

Station Address of originator

Channel

6 bit

0 – reserved for future use

Priority

2 bit

Priority between 0 (lowest) and 3 (highest)

Type

4 bit

Mailbox protocol types:

0x0: Error

0x1: Vendor specific (Beckhoff: AoE – ADS over EtherCAT)

0x2: EoE (Ethernet over EtherCAT)

0x3: CoE (CAN application layer over EtherCAT)

0x4: FoE (File access over EtherCAT)

0x5: SoE (Servo profile over EtherCAT)

0xF: Vendor specific (VoE)

Ctr.

3 bit

Sequence number that is used for detection of duplicated frames

Reserved

1 bit

8.3 PDI register function acknowledge by Write

Refer to chapter 16.2 for the background of this function, which only affects the SyncManager

operation when the PDI reads a buffer. The EtherCAT operation is not influenced by this optional

feature.

Reading a SyncManager buffer consists of the following steps, if PDI register function acknowledge by

Write is enabled:

 Read the first byte.

This will open the buffer. Accidentally reading subsequent bytes has no influence.

 Read any byte of the buffer.

This includes the first byte, the last byte, and any inner byte. The buffer remains open, and the

buffer can even be read multiple times. Accidentally reading the last byte has no influence.

 Write to the last byte of the buffer.

Byte enable signals are used, write data is ignored (write 0). This write operation closes the buffer.

Accidentally reading the first byte of a second SyncManager buffer behind the one to be read is still

possible, this will open the second SyncManager buffer. This can easily be prevented by aligning

SyncManager buffer start addresses to the data width of the µController. It is recommended to align

SyncManager buffer start addresses to 64 bit (8 byte) boundaries anyway.

8.4 Interrupt and Watchdog Trigger Generation, Latch Event Generation

Interrupts can be generated when a buffer was completely and successfully written or read. A

watchdog trigger signal can be generated to rewind (trigger) the Process Data watchdog used for

Digital I/O after a buffer was completely and successfully written. Interrupt and watchdog trigger

generation are configurable. The SyncManager Status register reflects the current buffer state.

For debugging purposes it is also possible to trigger Distributed Clock Latch events upon successful

buffer accesses (for some ESCs).

Ctr.

Type

Prio

Channel

Address

Length

16 Bit

6 Bit

2 Bit

4 Bit

3 Bit 1 Bit

1 2 ... 59 60 61 62 63 64 65 66 67 68 69 ... 115 116

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