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Contents of a Character (byte)
Each transferred character begins with a start bit. Subsequently, eight
data-bits are transferred, corresponding to one byte. Each character is
sent with a parity bit to produce even parity (i.e., an even number of
binary 1’s in the eight data-bits and the parity bit combined). A
character ends with a stop bit and therefore consists of a total of eleven
bits.
Start
0
1
2
3
4
5
6
7
Even Stop
bit
Parity Bit
Packet Buildup with FC Protocol
Each packet begins with a start character (STX) = 02 Hex, followed by
a byte that gives the packet length (LGE) and a byte that gives the
drive address (ADR). Next a number of data bytes is sent. The size of
the packet is variable, depending upon the packet type. The packet
ends with a data control byte (BCC).
STX
LGE
ADR
Data
BCC
Packet Times
The speed of communication between a master and a slave depends
on the baud rate. The baud rate of the drive must be the same as the
baud rate of the master. Select the baud rate of the drive in parameter
502, Baud Rate.
After a reply packet from the slave, there must be a minimum pause of two
characters (22 bits) before the master is able to send another packet. At a
baud rate of 9600 baud, there must be a minimum pause of 2.3 msec. After
the master has completed the packet, the response time of the slave back to
the master is a maximum 20 msec., with a minimum pause of two characters.
Pause time, minimum:
2 characters
Response time, minimum:
2 characters
Response time, maximum:
20 msec.
The time between individual characters in a packet is not to exceed two
characters, and the packet must be completed within 1.5 times the rated
packet time.If the baud rate is 9600 and the packet length is 16 baud,
the packet must be completed within 27.5 msec.
STX LGE ADR
DATA
BCC
= Time between characters
Packet Length (LGE)
The packet length is the number of data bytes plus address byte ADR
plus data control byte BCC.
Packets with four data bytes have a length of:
LGE = 4 + 1 + 1 = 6 bytes
Packets with twelve data bytes have a length of:
LGE = 12 + 1 + 1 = 14 bytes
Packets that contain text have a length of 10+n bytes. Ten is the fixed
characters, while ‘n’ is variable, depending on the length of the text.
Drive Address (ADR)
Two different address formats are used in which the address range of
the drive is either from 1 through 31 or from 1 through 126.
1.
Address format 1-31
The byte for this address range has the following profile:
7
6
5
4
3
2
1
0
0
Bit 7 = 0 (address format 1 through 31 active)
Bit 6 is not used
Bit 5 = 1: Broadcast, address bits (0 through 4), not used
Bit 5 = 0: No Broadcast
Bit 0 through 4 = Drive address 1 through 31
- - - - - -
- - - - - -
Pause
time
Response
time
Pause
time
Master
packet
Slave
packet