SERC816 데이터 시트보기 (PDF) - STMicroelectronics

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SERC816

SERCOS INTERFACE CONTROLLER

STMicroelectronics 

SERCON816

4.2.2 Data Containers

A data container comprises one or two 16-bit control words as well as a variable number of data words. If

the data is stored in the internal RAM (DMA = 0) and a single buffer is used (DBUF = 0), the data container

has one buffer. Using RAM storage and double buffering (DBUF = 1), two data buffers are needed. In case

of DMA transfer (DMA = 1) the data container only comprises the control words (Fig. 12). The structure of

the two control words depends on whether a telegram is transmitted or received:

Index Bit

Name

Function

0

0-9

LEN

Number of 16-bit data words of the data block.

10

SVFL

Flag, whether data block uses service container (SVFL = 1).

11-13

NSV

Number of service container, which is used (0 - 7).

14 SCMASTER Processing of service container in slave mode (SCMASTER = 0) or master mode

(SCMASTER = 1).

15

LASTDC Last data container of the telegram (1) or further data containers follow (0).

1

0-15

POS

Position of the data block within the telegram in number of words. The first data

record of a telegram has POS = 0 (only in case of receive telegrams).

Figure 12. Structure of Data Containers

DMA = 0, DBUF = 0

0 c ontrol word 0

1

buffer

DMA = 0, DBUF = 1

0 control word 0

1

buffer 0

DMA = 1

0 c ontrol word 0

1

LEN + 1

LEN + 1

buffer 1

2* LEN + 1

transm it

te leg ra m s

DMA = 0, DBUF = 0

0 c ontrol word 0

1 c ontrol word 1

2

buffer

DMA = 0, DBUF = 1

0 control word 0

1 control word 1

2

buffer 0

LEN + 2

LEN + 2

buffer 1

DMA = 1

0 c ontrol word 0

1 c ontrol word 1

2

rec eive

te leg ra m s

2* LEN + 2

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