Omega DPF20 Series User Manual

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DPF20 Frequency, rate, total or period counter Instruction Manual
2.4.4 Frame types
Protocol frames have a structure made of ‘Header’, ‘Data’ and ‘Trail’.
Secon ‘Header’
Contains the start byte (‘STX’), the frame idener (‘ID’), the origin
address (‘FROM’) and the desnaon address (‘TO’), the register id
(‘REG’) and the length (‘LONG’) of the ‘Data’ secon.
Secon ‘Data’
Contains data for the requested 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 Descripon Size Posion Real value Frame value
STX Start of frame 1 byte 0 does not apply 2
ID Frame type 1 byte 1 (see secon 2.4.4) real_value
RSV Reserved 1 byte 2 0 32
FROM Origin address 1 byte 3 0 (‘Master’) / 1 to 31 (‘Slave’) 32 + real_value
TO Desnaon address 1 byte 4 0 (‘Master’) / 1 to 31 (‘Slave’)
128 (‘broadcast’)
32 + real_value
REG Register idencaon 1 byte 5 (see secon 2.4.1) 32 + real_value
RSV Reserved 1 byte 6 0 32
LONG Length of ‘Data’ secon 1 byte 7 n (between 0 and 32) 32 + real_value
D0 … Dn Data n bytes 8 to n+7 number 0 to 9
decimal point
polarity (+/-)
ASCII code of the number (48 to 57)
ASCII code of decimal point (46)
ASCII code of ‘+’ (43)
ASCII code of ‘-’ (45)
CRC CRC calculaon 1 byte n+8 does not apply (see secon 2.4.8)
ETX End of frame 1 byte n+9 does not apply 3
Table 15 - Descripon of the bytes for the ASCII frame
Secon ‘Trail’
Contains the ‘CRC’ code and the end of frame byte (‘ETX’).
‘Real value’ and ‘Frame value’
To use representable ASCII values, the real values are codied before
being sent into the frame. The following denions apply :
• ‘real value’ is the value of the eld without codicaon
• ‘frame value’ is the value of the eld, codied
2.4.5 Frame structure
The ASCII protocol denes the following frames:
• Frame ‘read’ (‘RD’). Id code 36. Request data frame. The requested
register is indicated into the ‘REG’ byte (‘Header’ secon).
• Frame ‘answer’ (‘ANS’). Id code 37. Response frame to a request
data frame. The requested register is indicated into the ‘REG’ byte’
(‘Header’ secon). Data of the requested register is indicated into
data bytes ‘D0’ to ‘Dn’ (‘Data’ secon).
• Frame ‘error’ (‘ERR’). Id code 38. Response frame to a request data
frame. Indicates that an error has occurred. Error code is codied
into the ‘REG’ byte (‘Header’ secon).
• Frame ‘ping’ (‘PING’). Id code 32. Used to conrm the existence of
the remote instrument.
• Frame ‘pong’ (‘PONG’). Id code 33. Response to a ‘ping’ frame. It
conrms the existence of the remote instrument.
2.4.6 Error codes
Frames ‘ERR’ contain within the ‘REG’ eld, the error code. Available
error codes are :
error 1 unknown register
error 2 display overrange
error 3 display underrange
error 4 CRC error
error 5 internal error

Omega DPF20 Series Specifications

General

Brand	Omega
Model	DPF20 Series
Category	Measuring Instruments
Language	English