Frontier RUT-G 2005, Руководство пользователя

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Kele • RUT-G Manual 2005 • www.kele.com • USA 888-397-5353 • International 901-382-6084
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RS232/485 INTERFACE KEY
When the data packet has been successfully transmitted to the user device, the network interface key resets the RTS
to a low state. In turn, when the user device has received the full data packet (‘\r’ hex 0x0d is last byte in packet), it
must reset the CTS to a low state.
If the Packet Acknowledge (ACK) is enabled (see Definitions: PACKET ACKNOWLEDGE ENABLE/DISABLE), the
user device must send the ACK character to the network interface key acknowledging that the packet was received.
Transmitting RS232 to the Frontier Network Interface Key from the User Device
RTS and CTS are not supported when the user device is transmitting data to the network interface key. The network
interface key is designed to use communication input interrupts (interrupt driven) and buffers when receiving data
from the user device.
When the user device transmits data, the network interface key processor is interrupted and immediately starts to
read the incoming data packet. If the ACK is enabled, the network interface key will send the ACK character to the
user device acknowledging the packet was received with the exception of polled data. In polled applications, the re-
quested packet is the ACK.
Transmission Timeout Periods or Character Counts must be used to prevent data buffer overruns. If the end char-
acter is not detected (or not sent), these measures provide a means to stop transmitting or receiving.
The following example can be used for determining transmission timeouts. Not all devices allow users to set timeouts
for communication ports, but for those that do, the following is a good process to use.
This timeout period is based on individual data packets. It uses the baud rate and packet size:
Timeout = 1.5 * ((1/Baud) * 10 bits * number of bytes in data packet). The constant 1.5 value adds extra time for basic
processing and processor delays. If the timeout period is exceeded before the transmission is completed, the net-
work interface key or user device returning the CTS\RTS to a low state terminates the transmission.
For a 4800 baud rate and a 12 byte data packet (including start byte, end byte, and comma bytes), the Timeout Period
is approximately 38 mS. For a 9600 baud rate and a 12 byte data packet, the Timeout Period is approximately 19 mS.
For a 19,200 baud rate and a 12 byte data packet, the Timeout Period is approximately 10 mS. Because data packet
transmissions vary by byte count, the timeout values must be calculated before each transmission.
Other means of control can also be used. Since data packet sizes are not known when receiving, this prohibits using
a timeout based on packet size. Instead, test with character counting, based on the maximum byte count possible
in the largest data packet (40 characters is a good number). As an alternative, or in addition to character counting,
a fixed maximum timeout can be used. Use 100 milliseconds for 4800 baud, 50 milliseconds for 9600 baud, and 30
milliseconds for 19,200 baud. These values allow buffering time for processing and may need to be adjusted depend-
ing on the application.
RS485 Communication
RS485 Master/Slave
The RS485 Frontier Gateway network interface key software is designed for Master/Slave operation with the user’s
device as the master.
RS485 Addressing
The Interface Key must be set with a unique address on the Node Address Dip Switch located on the network inter-
face key. Refer to Table 6 for value settings. This address must be included in all transmissions to the Gateway and
will be included in all transmissions to the user’s device.
COMMUNICATION WIRING
IMPORTANT:
The network interface key will not transmit again until it sees the CTS line go to a low state from the previous
transmission.