Omega DPF20 Series User Manual (English)

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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

• 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

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Omega DPF20 Series Specifications

General

Accuracy	±0.25% FS
Operating Temperature	-20 to 85°C (-4 to 185°F)
Display	LCD
Power	9 to 30 Vdc
Measurement Range	0 to 1000 psi
Output	4 to 20 mA
Power Supply	12-30 VDC
Process Connection	1/4 NPT male
Housing Material	Stainless Steel
Diaphragm Material	316L stainless steel