BECKHOFF EtherCAT IP Core for Xilinx FPGAs v3.00k - Manual (Page 123)

PDI Description
Slave Controller – IP Core for Xilinx FPGAs III-111
10.3.6 µController access errors
These reasons for µController access errors are detected by the µController interface:

Read or Write access to the 16 bit interface with A[0]=1 and BHE(act. low)=1, i.e. an access to an
odd address without Byte High Enable.

Deassertion of WR (or deassertion of CS while WR remains asserted) while the µController
interface is BUSY.

Deassertion of RD (or deassertion of CS while RD remains asserted) while the µController
interface is BUSY (read has not finished).
A wrong µController access will have these consequences:

The PDI error counter 0x030D will be incremented.

For A[0]=1 and BHE(act. low)=1 accesses, no access will be performed internally.

Deassertion of WR (or CS) while the µController interface is BUSY might corrupt the current and
the preceding transfer (if it is not completed internally). Registers might accept write data and
special functions (e.g., SyncManager buffer switching) might be performed.

If RD (or CS) is deasserted while the µController interface is BUSY (read has not finished), the
access will be terminated internally. Although, internal byte transfers might be completed, so
special functions (e.g., SyncManager buffer switching) might be performed.
The reason of the access error can be read in the PDI error code register 0x030E.
10.3.7 Connection with 16 bit µControllers without byte addressing
If the ESC is connected to 16 bit µControllers/DSPs which only support 16 bit (word) addressing,
ADR[0] and BHE of the EtherCAT device have to be tied to GND, so the ESC will always perform 16
bit accesses. All other signals are connected as usual. Please note that ESC addresses have to be
divided by 2 in this case.
CS CS
ADR[14:0]
RD
BUSY
DATA[15:0]
WR
ADR[15:1]
ADR[0]
RD
BUSY
DATA[15:0]
WR
16 bit µController, async,
only 16 bit addressing
EtherCAT device
IRQ IRQ
BHE
General purpose input EEPROM_Loaded
optional
Figure 51: Connection with 16 bit µControllers without byte addressing