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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:

Figure 12. Structure of Data Containers

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).

c ontrol word 0

c ontrol word 0

c ontrol word 1

control word 0

control word 0

control word 1

c ontrol word 0

c ontrol word 0

c ontrol word 1

buffer

buffer

buffer 0

buffer 0

buffer 1

buffer 1

0

0

1

0

0

1

0

0

1

1

2

1

2

1

2

LEN + 1

LEN + 2

LEN + 1

LEN + 2

2* LEN + 1

2* LEN + 2

DMA = 0, DBUF = 0

DMA = 0, DBUF = 0

DMA = 0, DBUF = 1

DMA = 0, DBUF = 1

DMA = 1

DMA = 1

transm it

telegra ms

rec eive

telegra ms