902B Abs Piezo
Operation manual
13
Baud rate
The baud rate represents the communication speed. The 902B supports 4800, 9600, 19200, 38400, 57600,
115200 and 230400 baud rates. The transducer is always delivered with 9600 bps factory default baud rate.
Change of Baud rate:
Command:
@253BR!19200;FF
Command values:
4800, 9600, 19200, 38400, 57600, 115200, 230400
Command reply:
@253ACK19200;FF
Factory default:
9600
The transducer will reply in the current baud rate and then change to the new value.
Addressing
The transducer uses an addressable communication protocol that allows multiple MKS 900 Series
transducer devices to be connected in a RS485 network. The address is required in both RS232 and RS485
communication.
The address can be set from 001 to 253. Address 254 and 255 are universal addresses, which can be used
to broadcast a command to all devices on the network. Commands sent with address 254 will be executed
by all transducers on the network and all transducers will transmit a reply. Commands sent with address 255
will be executed by all transducers on the network, but the transducers will not transmit replies. For example,
use address 254 to communicate with a device if its address is unknown.
Change of Address:
Command:
@253AD!123;FF
Command values:
001 to 253
Command reply:
@253ACK123;FF
Query:
@253AD?;FF
Query reply:
@253ACK253;FF
Factory default:
253
Communication delay (RS485)
The 902B half-duplex RS485 interface requires that data is transmitted and received on the same
communication line. Some RS485 transceiver equipment has a settling time when changing from transmit to
receive mode. If the transducer replies too fast the first character(s) will not be received as the following
example illustrates:
Sending pressure request: @254PR1?;FF
Receiving data:.
64;FF (Correct data: @253ACK764;FF)
The RS delay introduces a baud rate dependent delay between receive and transmit sequence to prevent
loss of data in the receiving string.
Communication delay:
Command:
@253RSD!ON;FF
Command values:
ON, OFF
Command reply:
@253ACKON;FF
Query:
@253RSD?;FF
Query reply:
@253ACKON;FF
Factory default:
ON