Figure 6.12-15 Rs-485 Nrts Driving Level In Auto Direction Mode; Figure 6.12-16 Rs-485 Nrts Driving Level With Software Control - Nuvoton ISD94124BYI Technical Reference Manual

nRTS pin output status of RS-485 function mode (RS-485 AUD mode enabled)
TX pin output
RTSSTS
(UART_MODEM[13])
nRTS pin output
Note: RS485AUD(UART_ALTCTL[10]) = 1, the nRTS pin output by hardware control only.

Figure 6.12-15 RS-485 nRTS Driving Level in Auto Direction Mode

Figure 6.12-16 demonstrates the RS-485 nRTS driving level in software control (RS485AUD
(UART_ALTCTL[10])=0).
RTS(UART_MODEM[1]) control bit.
Setting RTSACTLV (UART_MODEM[9]) can control the nRTS pin output is inverse or non-inverse
from RTS(UART_MODEM[1]) control bit. User can read the RTSSTS (UART_MODEM[13]) bit to
get real nRTS pin output voltage logic status.
nRTS pin output status of RS-485 function mode
Set UART_MODEM[1]=0 by software
RTS control bit
(UART_MODEM[1])
RTSACTLV = 0
RTSSTS
(UART_MODEM[13])
nRTS pin output
RTSACTLV = 1
Note: RS485AUD (UART_ALTCTL[10]) = 0, support nRTS control bit by software control only.

Figure 6.12-16 RS-485 nRTS Driving Level with Software Control

Programming Sequence Example:
1. Program FUNCSEL in UART_FUNCSEL to select RS-485 function.
2. Program the RXOFF (UART_FIFO[8]) to determine enable or disable the receiver RS-
485 receiver.
3. Program the RS485NMM (UART_ALTCTL[8]) or RS485AAD (UART_ALTCTL[9]) mode.
4. If the RS485AAD (UART_ALTCTL[9]) mode is selected, the ADDRMV
(UART_ALTCTL[31:24]) is programmed for auto address match value.
Sep 9, 2019
ISD94100 Series Technical Reference Manual
Start
D0 D1
bit
RTSACTLV = 0
RTSACTLV = 1
(default)
The nRTS driving
(default)
Page 586 of 928
D2 D3 D4 D5 D6 D7
Driver Enable
level is controlled by
Set UART_MODEM[1]=1 by software
Active
Driver Enable
Stop
P
bit
programing the
Rev1.09