Danfoss VLT 2800 Manual de Serviço descarregar pdf (Página 116)

Telegram length (LGE)

The telegram length is the number of data bytes plus

the address byte ADR plus the data control byte BCC.

The length of telegrams with 4 data bytes is:

LGE = 4 + 1 + 1 = 6 bytes

The length of telegrams with 12 data bytes is:

LGE = 12 + 1 + 1 = 14 bytes

The length of telegrams containing texts is 10+n bytes.

10 represents the fixed characters, while the 'n' is var-

iable (depending on the length of the text).

Frequency converter address (ADR)

Two different address formats are used, with the fre-

quency converter's address range being either 1-31 or

1-126.

1. Address format 1-31

The byte for address range 1-31 has the following pro-

file:

Bit 7 = 0 (address format 1-31 active)

Bit 6 is not used

Bit 5 = 1: Broadcast, address bits (0-4) are

not used

Bit 5 = 0: No Broadcast

Bit 0-4 = Frequency converter address 1-31

2. Address format 1-126

The byte for address range 1 - 126 has the following

profile:

Bit 7 = 1 (address format 1-126 active)

Bit 0-6 = Frequency converter address 1-126

Bit 0-6 = 0 Broadcast

The slave sends the address byte back unchanged in

the response telegram to the master.

Example:

writing to frequency converter address 22 (16H) with

address format 1-31:

Data control byte (BCC)

The data control byte is explained in this example:

Before the first byte in the telegram is received, the

Calculated CheckSum (BCS) is 0.

When

the first byte (02H) has been received:

BCS = BCC EXOR “first byte”

(EXOR = exclusive-or)

BCS = 0 0 0 0 0 0 0 0 (00 H)

EXOR

1. byte

= 0 0 0 0 0 0 1 0 (02H)

BCC = 0 0 0 0 0 0 1 0 (02H)

Each subsequent byte gates with BCS EXOR and pro-

duces a new BCC, e.g.:

BCS = 0 0 0 0 0 0 1 0 (02H)

EXOR

2nd byte

= 1 1 0 1 0 1 1 0 (D6H)

BCC = 1 1 0 1 0 1 0 0 (D4H)

VLT

2800 Series

116 MG.27.E3.02 - VLT

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