Rockwell-automation 1797-OE8H FLEX Ex HART Analog Modules User Manual Uživatelský manuál stáhnout pdf (Strana 153)

Publication 1797-6.5.3 - March 2006

Additional HART Protocol Information C-5

Response Code

This two-byte code contains the HART field device status as sent by that

device. Field devices detecting a communications error set the most significant

bit, bit 7, of the first byte and identify the error in the other seven bits. If the

last message was received without error, the field device will clear bit 7 and

return a device-dependent response in the other seven bits.

The second byte of this response code returns the operating status of HART

field devices. This byte may default to 0 when a communications error occurs

as indicated by bit 7 of the first byte being set.

IMPORTANT

The host controller ignores any values in the data

field when a communications error is detected.

Table C.3 HART Protocol — Communication Error Code

Bit Error Code Description

7 Communications error If set, the field device has detected a

communications error. Bits 0…6 indicate the

type of error.

6 Vertical parity error The parity of one or more of the bytes received

by the HART field device is incorrect.

5 Overrun error At least one byte of data in the receive buffer of

the HART field device was over-written before it

was read.

4 Framing error The stop bit of one or more bytes received by the

HART field device was not detected.

3 Longitudinal parity error The longitudinal parity calculated by the HART

field device does not match the longitudinal

parity byte at the end of the packet.

2 Reserved Set to 0.

1 Buffer overflow The packet is too long for the receive buffer of

the HART field device.

0 Undefined Not defined.

1 2 ... 148 149 150 151 152 153 154 155 156 157 158 ... 195 196

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Rockwell-automation 1797-OE8H FLEX Ex HART Analog Modules User Manual Uživatelský manuál Strana 153