Banner SureCross DX80 Series Manual page 11

SureCross™ FlexPower™ Data Radio
Overview
After powering up, the data radio begins standard operating mode, known as RUN mode. When in RUN mode, the radio receives data from the
serial port RS485 interface and transmits that data as a radio frequency (RF) packet. Received RF packets are demodulated to baseband and
transmitted through the serial port.
Timing
As data enters the serial port, it is queued up in a 255-byte buffer until there is a break in the bitstream that indicates the end of a packet. Once
a suitable break is measured, the data packet moves into a second 255-byte buffer. The radio transmitter sends the packet over the air.
At the receiver, the demodulated data is stored in a buffer that is the same size as the original data packet. Once the complete data packet has
been received, it is sent uninterrupted through the serial port. The net effect of the cascaded buffering, transmitting, and receiving is that serial
packets emerge from the data radio delayed but unchanged.
To prevent data loss during serial transmission, packet sizes should be limited to 255 bytes. The inactivity between packets must be at least
3.6 milliseconds.
For non-Modbus applications, once the minimum inactivity time to delimit a packet is met, users must still consider the time required to transmit
the packet over the air to avoid overrunning the buffers. For the best results, run at the higher (76.8 kb/s) data rate over the air and consult the
factory for application-specific guidance.
Packet Counting
Part of the RUN mode display is dedicated to displaying a cumulative total of serial packets sent and received. A sent packet is transmitted out
the wired serial lines. A received packet is received on the wired serial port. The packet counter increments when a valid break in the data is
measured, as discussed in the timing section above. The counter values reset when power cycles to the device or may be manually reset by
quadruple-clicking button 2, then using button 1 to choose which values to reset and button 2 to initiate clearing the value. To exit this feature
without clearing a value, double-click button 2.
The packet counts are kept in a 32-bit register capable of holding over 4 billion counts before rolling over. Because the display is limited to
six digits, values over 999,999 display across two successive LCD screens, the first of which is denoted by a leading '+' sign. For example, a
count value of 12,345,678 displays as '+ 12' and then '345678' on the next screen.
Power Supplies
The data radio can accept two types of dc power sources. Use the brown wire to supply +10 to 30V dc to the device. Use the gray wire to
power the data radio from a low-voltage source. This voltage must not exceed 5.5V dc or the data radio will be damaged.
When both a +10–30V dc and a 3.6–5.5V dc voltage are present, the circuitry automatically selects the source. The gray wire supply is the
power source when its voltage is greater than 3.4V dc. Even when the gray wire supplies the power, there will be a quiescent draw on the
brown wire of about 5 mA. The 3.4V dc threshold is not a controlled parameter and some current sharing may occur when the gray wire is near
this threshold.
Banner Engineering Corp. • Minneapolis, MN U.S.A
10
www.bannerengineering.com • Tel: 763.544.3164
P/N 132031 rev. E