ISD94100 Series Technical Reference Manual
Sep 9, 2019
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Rev1.09
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ER
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HN
ICA
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RE
NCE
M
AN
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AL
D0
D1
D2
D3
D4
D5
D6
D7
P
Start
bit
Stop
bit
TX pin output
(default)
Driver Enable
nRTS pin output status of RS-485 function mode (RS-485 AUD mode enabled)
RTSACTLV = 0
RTSACTLV = 1
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). The nRTS driving level is controlled by programing the
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.
Active
nRTS pin output status of RS-485 function mode
(default)
Driver Enable
Set UART_MODEM[1]=0 by software
Set UART_MODEM[1]=1 by software
RTS control bit
(UART_MODEM[1])
RTSSTS
(UART_MODEM[13])
nRTS pin output
RTSACTLV = 0
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.