Beckhoff EtherCAT Technology Section I Bedienungsanleitung PDF herunterladen (Seite 59)

FMMU

Slave Controller – Technology I-39

7 FMMU

Fieldbus Memory Management Units (FMMU) convert logical addresses into physical addresses by

the means of internal address mapping. Thus, FMMUs allow to use logical addressing for data

segments that span several slave devices: one datagram addresses data within several arbitrarily

distributed ESCs. Each FMMU channel maps one continuous logical address space to one continuous

physical address space of the slave. The FMMUs of Beckhoff ESCs support bit wise mapping, the

number of supported FMMUs depends on the ESC. The access type supported by an FMMU is

configurable to be either read, write, or read/write.

Figure 20: FMMU Mapping Principle

The following example illustrates the functions of an FMMU configured to map 14 bits from logical

address 0x00010011.3 to 0x00010013[0] to the physical register bits 0x0F01[1] to 0x0F02[6]. The

FMMU length is 3 Byte, since the mapped bits span 3 Bytes of the logical address space. Length

calculation begins with the first logical byte which contains mapped bits, and ends with the last logical

byte which contains mapped bits.

Table 22: Example FMMU Configuration

FMMU configuration register

FMMU reg. offset

Value

Logical Start Address

0x0:0x3

0x00010011

Length (Bytes)

0x4:0x5

Logical Start bit

0x6

Logical Stop bit

0x7

Physical Start Address

0x8:0x9

0x0F01

Physical Start bit

0xA

Type

0xB

read and/or write

Activate

0xC

1 (enabled)

NOTE: FMMU configuration registers start at address 0x0600.

Logical process image: up to 4 GByte

Telegram structure

Ethernet HDR HDR 1 PLC Data HDR 2 NC Data HDR n Data n FCS

PLC Data

Data n

NC Data

DVI

IPC

Sub-

Telegram 1

Sub-

Telegram 2

Sub-

Telegram n

1 2 ... 54 55 56 57 58 59 60 61 62 63 64 ... 115 116

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