Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Uživatelský manuál stáhnout pdf (Strana 42)

3–5Using Half-duplex Protocols to Send and Receive Messages

Publication

17706.5.16 - October 1996

GETMESSAGE

is defined as

GET-CODE

while it is data code

begin

if buf

fer is not overflowed put data in buf

fer

GET-CODE

end

if it is a control code and it is an ETX then

begin

if parity error flag is set then return a NAK

if BCC is not zero then return a NAK

if message is too small then return a NAK

if message is too large then return a NAK

return an ACK

end

else end

GET-CODE is defined as

loop

variable

GET-CHAR

if char is not a DLE

begin

add char to BCC

return the char and a data flag

end

else

begin

GET-CHAR

if char is a DLE

begin

add char to BCC

return a DLE and a data flag

end

else if char is an ETX

begin

GET-CHAR

add char to BCC

return ETX with a control flag

end

else return char with a control flag

end

GETCHAR is defined as

an implementationdependent function that returns one byte of data

from the link interface hardware

SEND (Message) is defined as

begin

BCC = 0

send DLE STX

for every byte in the message do

begin

subtract the byte from the BCC

send the corresponding data code

end

send DLE ETX BCC

end

1 2 ... 37 38 39 40 41 42 43 44 45 46 47 ... 250 251

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Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Uživatelský manuál Strana 42

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