A
RF53
User Guide
Ref.
08-07-V6-lmn
p
8
By default the DE and RE lines are asserted LOW, allowing receiving
character from the RS485 differential bus. The DE and RE lines are asserted
HIGH only when one or several characters have to be transmitted over the
RS485 differential bus: when a radio frame is demodulated, the lines are
asserted HIGH and then the data extracted from the radio frame are sent to
the module TXD line and therefore to the RS485 differential bus. When the
last character has been transmitted over the RS485 differential bus, the lines
are asserted LOW.
Figure 2 : DE/RE timing when data are sent over the serial link
Threshold: minimum = 1 µs
Tde: set according to the S219 register value (see table hereafter)
S219 0 1 2 3 4 5 10 20 40 60 80
Tde
min
15
µs
35
µs
65
µs
135
µs
150
µs
190
µs
330
µs
600
µs
1,1
ms
1,7
ms
2,3
ms
In command mode, a reply is sent back (on the TXD line) according to the
following DE/RE timing:
The RS485 link needs to be adapted (each side). The modem includes a
100
Ω
termination resistor:
SW1.2 = ON, the resistor is connected between A and B (respectively RX+
and RX-)
SW1.2 = OFF, the resistor is not connected between A and B.
If the modem is ending the RS485 bus, SW1.1 must be ON.
TOP
