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DIGITAL-LOGIC AG
4
D
ETAILED
4.1
Programming the RS422/485 port
On the RS422/485-port the signals of UART have the following functions:
Signal of UART
RxD
RTS
TxD
The /RE is harware straped to low, and the receiver is always enabled.
Typical Application
Summary
If the UART should transmit, then set the Bit RTS in the modem control register to '0' before the databyte
is sent to the transmit register.
If the UART should receive, wait on the receive buffer full flag as usual. Nothing special must be done,
since the RS422/485 receiver is always enabled.
FUNCTION TABLES
ADM489 Transmitting
INPUTS
/RE = GND
TE=RTS
0
0
0
0
ADM489 Receiving
INPUTS
/RE = GND
TE=RTS
0
0
S
YSTEM
DI
1
1
1
0
0
X
1
X
A - B
1
≥ + 0.2V
1
≤ - 0.2V
D
ESCRIPTION
Function of RS485
RO (Receive Line)
DE (Transceiver enable) 1=Enable, 0= Tristate
DI (Transmission line)
Line
Condition
no fault
no fault
X
fault
OUTPUTS
R
1
0
15
MSMX104 Manual V1.3
OUTPUTS
B
A
0
1
1
0
Z
Z
Z
Z
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