User`s manual

Western Reserve Controls, Inc. 1782-JDC User’s Manual

If Max_Number_of_Receive_Chars > 0 (Param. 5),

The expected operation is that the JDC receives characters (data bytes) until the

delimiter character is received

If a delimiter is received, then

 All characters up to and including the defined delimiter are sent to the DeviceNet

master, and

o If Pad Mode = 1, then the JDC will fill the Poll Response data with the

Pad Char defined in Param. 9, up to the defined size

o If Pad Mode = 0, then the JDC will send only the data up to and including

the delimiter

If no delimiter is received, then

 The JDC will receive up to Max_Number_of_Receive_Chars, and then sends this

string to DeviceNet with an overflow error

 If will continue to receive and send strings of size

Max_Number_of_Receive_Chars, along with the overflow error, until a delimiter is

received. This could continue indefinitely if your ASCII device does not transmit

the specified delimiter.

5.2 Setting up DeviceNet Communications

The 1782-JDC supports 3 modes of data transfer of the serial buffer. They are:

 Polled

 Change-of-state

 Cyclic

5.2.1 Polled I/O

The polled connection is the only manner in which you can send serial output data to the

JDC and, therefore, to your ASCII device. The DeviceNet Master initiates the polled

connection transfer. The Master sends the JDC its serial output buffer along with a record

number and length byte. The JDC monitors for a change in the record number. If the record

number changes, then the 1782-JDC transmits the data buffer on its serial link. If the record

number does not change, then the device does not transmit the data buffer.

After the device has transmitted its data out to the serial link, the JDC then takes any

information that is stored in its current serial input buffer and sends this data to the DeviceNet

Master. It sends all characters up to and including the received delimiter, padding only if

specified in the parameter object. When the JDC receives a new message (either with a

delimiter or with an overflow condition without a delimiter) the device then increments the

receive record, updates the length byte, and copies the new information from the last receive

delimiter into the buffer. If an overflow occurs, the JDC indicates so in its receive status bit.

The receive status byte also reflects parity errors in the device. (See Table 2-3.)

5.2.2 Cyclic and Change-of-State I/O

The Cyclic connection initiates a transmission every time the connection timer expires.

This is explained below in the Section 5.2.4. The cyclic connection can only send data from