A6175 ROC800-Series Remote Operations Controller Instruction Manual

ROC800-Series Instruction Manual

4-32

Input/Output Modules

Revised Jul-14

commands conform to HART Universal Command Specification

Revision 5.1 and Common Practice Command Specification Revision 7,

(HCF SPEC 127 and 151). Refer to

www.hartcomm.org

for more

information on the specifications.

The HART-2 module polls the channels simultaneously. If more than

one device is connected to a channel in a multi-drop configuration, the

module polls one device per channel at a time. The HART protocol

allows one second per poll for each device, so with five devices per

channel the maximum poll time for the channel would be five seconds.

Note

The ROC800

does not

support HART devices configured in

Burst mode (in which the device sends information without a

prior request). If you have a HART device configured in burst

mode, use a hand-held field communicator to turn off burst

mode

before

you connect the device to the ROC800.

The HART-2 module provides “loop source” power (+T) and four

channels (1+ through 4+) for communications. The +T power is current-

limited.

ROC-powered

HART Devices

When using the ROC800 to power HART devices, connect terminal

+T in parallel to the positive (+) terminal on all of the HART devices,

regardless of the channel to which they are connected.

Wire channel 1+ to the negative (–) terminal of a single HART device,

or in parallel to the negative terminals of the devices. Likewise, wire

channel 2+ to the negative (–) terminal of a single HART device, or in

parallel to the negative terminals of a second group of HART devices

(see

Figure 4-40

Externally powered

HART Devices

When powering HART devices by an external device, connect the

positive (+) terminal from the power source in parallel to the positive

(+) terminal on all of the HART devices, regardless of the channel to

which they are connected.

Wire channel 1+ on the HART-2 module to the positive (+) terminal of

the HART device. Connect the power source negative (–) terminal to

the channel’s COM terminal and to the negative (–) terminal of a single

HART device, or in parallel to the negative terminals of the HART

devices.