APC 6000 Manual De Usuario
6739389EN/FB
- Page 7
JBUS protocol
(continued)
Principle
A full understanding of the protocol
is only required if the master is a
computer that must be
programmed.
is only required if the master is a
computer that must be
programmed.
All communications include 2
messages: a request from the
master and a response from the
slave.
messages: a request from the
master and a response from the
slave.
Each message or frame containes
4 types of information:
4 types of information:
◗
slave address (1 byte)
The slave address specifies the
destination station (see address
list):
destination station (see address
list):
◗
◗
unitary rectifier-inverter cubicle,
◗
◗
parallel rectifier-inverter cubicle,
◗
◗
Static Switch cubicle.
If zero, the request addresses all
slaves and there is no response
message (in which case it is a
broadcast message, a function not
used in this application);
slaves and there is no response
message (in which case it is a
broadcast message, a function not
used in this application);
Synchronizing data
exchanges
exchanges
Any character received after 3 or
more character lengths of silence is
interpreted as the start of a frame.
Therefore, a minimum silence of 3
character lengths between frames
must be respected.
more character lengths of silence is
interpreted as the start of a frame.
Therefore, a minimum silence of 3
character lengths between frames
must be respected.
◗
function code (1 byte)
Selects a command (e.g. read or
write a bit or a word) and checks
that the response is correct.
The JBUS protocol comprises 10
functions of which 3 may be used in
this application: function 3 (read n
output or internal words), or
function 4 (read n input words), or
function 16 (write n words);
write a bit or a word) and checks
that the response is correct.
The JBUS protocol comprises 10
functions of which 3 may be used in
this application: function 3 (read n
output or internal words), or
function 4 (read n input words), or
function 16 (write n words);
◗
information field (n bytes)
The information field contains the
parameters related to the functions:
bit address, word address, bit
value, word value, number of bits,
number of words;
parameters related to the functions:
bit address, word address, bit
value, word value, number of bits,
number of words;
◗
check word (2 bytes)
A word used to detect transmission
errors.
errors.
Description of request and response frames
information
check word
request
1 byte
1 byte
n bytes
2 bytes
When the message is
received, the slave reads
the check word and accepts
or refuses the message
received, the slave reads
the check word and accepts
or refuses the message
This function code selects one of
10 possible commands:
- Function 1 : read n output or internal bits
- Function 2 : read n input bits
- Function 3 : read n output or internal words
- Function 4 : read n input words
- Function 5 : write one bit
- Function 6 : write one word
- Function 8 : data exchange diagnostics
- Function 11 : read event counter
- Function 15 : write n bits
- Function 16 : write n words
10 possible commands:
- Function 1 : read n output or internal bits
- Function 2 : read n input bits
- Function 3 : read n output or internal words
- Function 4 : read n input words
- Function 5 : write one bit
- Function 6 : write one word
- Function 8 : data exchange diagnostics
- Function 11 : read event counter
- Function 15 : write n bits
- Function 16 : write n words
information requested: bit/word address,
bit/word value, bit/word number.
bit/word value, bit/word number.
slave adress
(1 à FF)
(1 à FF)
function
code
code
data
response
values of bits or words read
values of bits or words written
number of bits or words
values of bits or words written
number of bits or words
slave adress
(1 à FF)
(1 à FF)
function
code
code
CRC
check word
check word
2 bytes
◗
bytes
1 byte
1 byte