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Function 3 and 4: read N words
The number of words must be less
than or equal to the word field size
(see memory board).
◗ function 3: read output or internal
words;
◗ function 4: read input words.
request
1 byte
1 byte 1 byte
1 byte
1 byte 2 bytes
2 bytes 2 bytes
slave address
3 or 4
slave address
3 or 4
CRC 16
CRC 16
response
2 bytes 2 bytes
2 bytes
example
first word
PF pf
last word
PF pf
adress of
first bit
MSB LSB
number of
words
MSB LSB
number of
bytes read
Function 5: writing a bit
request:
response:
word 0146
word 014B
Reading words at location 146 to 14B of slave at address 28H (voltage fields)
03 0146 06 A7 E0
28
28
03 0C XXXX YYYY CRC 16
request
slave address 5
1 byte
1 byte 2 bytes 2 bytes1 byte 1 byte
bit address
bit value 0 CRC 16
slave address 5
bit address
bit value 0 CRC 16
In function 5 the response and request frames are identical.
response
example
request:
Setting bit location C05 to 1 of slave at address 40H (inverter on)
05 0C05 FF 0040
90 7A
write 0
write FF
bit set to 0
bit set to 1
JBUS protocol (continued)