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NIM Primitives

4-3

TIWAY 1 Ti505 NIM User Manual

Figure 1

illustrates the basic Primitive structure when HDLC operation is selected.

There

is a Request Format and a Response Format, as shown. The binary weight of the

fields is detailed in Figure 2. All field lengths are multiples of 8 bits, which allows for

octet

testing of data link frames at the data link/media access control layer

HDLC I Frame or UI Frame

Flag Address Control Information FCS Flag

Bit

0 8 16 24 N – 24 N – 8 N

Length

Primitive Code Descriptor(s)Data Unit(s)

Primitive Fields

Request Format

Response Format

MSB

LSB

Length Prim / Error Secondary StatusData Unit(s)

Figure 1

Basic Primitive Structure

The

maximum length of the Information field is 273

bytes for the Series 505



NIM.

the

Request, the 273 bytes include the Length, Primitive code, Descriptor, and Data Unit

fields.

In the Response, the 273 bytes include the Length, Primitive Code/Error

, Secon

dary Status, and Data Unit fields. In both formats, the 273 bytes exclude the protocol

control

fields. The actual length supported is dependent on the attached

device type and

must

be ascertained with the Format Configuration Primitive 04.

1 2 ... 56 57 58 59 60 61 62 63 64 65 66 ... 117 118

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Siemens SIMATIC TIWAY 1 Bedienungsanleitung Seite 61