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M451
May. 4, 2018
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RS-485 Auto Direction Function (AUD)
Another option function of RS-485 controllers is RS-485 auto direction control function
(RS485AUD (UART_ALTCTL[10) = 1). The RS-485 transceiver control is implemented by using
the nRTS control signal from an asynchronous serial port. The nRTS line is connected to the RS-
485 transceiver enable pin such that setting the nRTS line to high (logic 1) enables the RS-485
transceiver. Setting the nRTS line to low (logic 0) puts the transceiver into the tri-state condition to
disabled. User can set RTSACTLV in UART_MODEM register to change the nRTS driving level.
The Figure 6.13-21 demonstrates the RS-485 nRTS driving level in AUD mode. The nRTS pin will
be automatically driven during TX data transmission.
Setting RTSACTLV(UART_MODEM[9]) can control nRTS pin output driving level. User can read
the RTSSTS(UART_MODEM[13]) bit to get real nRTS pin output voltage logic status.
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])
RTS pin output
Note:
RS485AUD(UART_ALTCTL[10]) = 1, the nRTS pin output by hardware control only.
Figure 6.13-21 RS-485 nRTS Driving Level in Auto Direction Mode
The Figure 6.13-22 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])
RTS pin output
RTSACTLV = 0
RTSACTLV = 1
Note:
RS485AUD (UART_ALTCTL[10]) = 0, support nRTS control bit by software control only.
Figure 6.13-22 RS-485 nRTS Driving Level with Software Control
Содержание ARM Cortex NuMicro M451 Series
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Страница 355: ...M451 May 4 2018 Page 355 of 1006 Rev 2 08 M451 SERIES TECHNICAL REFERENCE MANUAL 2 0 Reserved Reserved...
Страница 625: ...M451 May 4 2018 Page 625 of 1006 Rev 2 08 M451 SERIES TECHNICAL REFERENCE MANUAL 00 5 bits 01 6 bits 10 7 bits 11 8 bits...
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Страница 1003: ...M451 May 4 2018 Page 1003 of 1006 Rev 2 08 M451 SERIES TECHNICAL REFERENCE MANUAL LQFP 48L 7x7x1 4mm footprint 2 0mm 9 4...