Fema Electronica K Series, User Manual, Page: 7 / 32

FEMA ELECTRÓNICA . Series K . K40-232
7
The protocol frames are structure with a header section (‘Header’), a
data section (‘Data’) and a end of frame section (‘Trail’).
Section ‘Header’
Contains the start of frame byte (‘STX’), the frame identifier (‘ID’),
the sender (‘FROM’) and destination (‘TO’) addresses, the register
number (‘REG’) and the length (‘LONG’) of the ‘Data’ section.
Section ‘Data’
Contains the data of the register (‘REG’).
Header Data Trail
STX ID RSV FROM TO REG RSV LONG D0 D1 ... Dn CRC ETX
2 x 32 x x x 32 n+1 [data] x 3
0 1 2 3 4 5 6 7 8 9 ... n+7 n+8 n+9
Field Description Size Position Real value Frame value
STX Start of frame 1 byte 0 does not apply 2
ID Type of frame 1 byte 1 (see section 1.13) real_value
RSV Reserved 1 byte 2 0 32
FROM Sender address 1 byte 3 0 (‘Master’) / 1 a 31 (‘Slave’) 32 + real_value
TO Destination address 1 byte 4 0 (‘Master’) / 1 a 31 (‘Slave’)
128 (‘broadcast’)
32 + v
REG Register number 1 byte 5 see sections 1.16, 1.17 and 1.18 32 + real_value
RSV Reserved 1 byte 6 0 32
LONG Length of ‘Data’ section 1 byte 7 n (between 0 and 32) 32 + real_value
D0 … Dn Data n bytes 8 a n+7 number 0 to 9
decimal point
sign (+/-)
ASCII code for number (48 to 57)
ASCII code for dot (46)
ASCII code for ‘+’ (43)
ASCII code for ‘-’ (45)
CRC CRC calculated value 1 byte n+8 does not apply (see section 1.19)
ETX End of frame 1 byte n+9 does not apply 3
Table 2 - Description of the ASCII frame bytes
Section ‘Trail’
Contains the ‘CRC’ code and the end of frame byte (‘ETX’).
‘Real value’ and ‘Frame value’
In order to use frame characters that are representable and easily
recognizable on screen, the protocol codifies the values before intro -
ducing them into the frame. The following nomenclature is defined :
• ‘real value’ is the value of the field without codification
• ‘frame value’ is the value codified
1.14 Frame structure