NuMicro® NUC029LEE/NUC029SEE
32-bit Arm
®
Cortex
®
-M0 Microcontroller
Aug, 2018
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Setting LEV_RTS(UA_MCR[9]) can control RTS pin output driving level. User can read the
RTS_ST(UA_MCR[13]) bit to get real RTS pin output voltage logic status.
LEV_RTS = 0
LEV_RTS = 1
RTS pin output status of RS-485 function mode (RS-485 AUD mode enabled)
D0
D1
D2
D3
D4
D5
D6
D7
P
Start
bit
Stop
bit
TX pin output*
RTS_ST
(UA_MCR[13]),
RTS pin output
(default)
Driver Enable
Note:
RS485_AUD(UA_ALT_CSR[10]) = 1, the RTS pin output by hardware control only.
Figure 6.13-17 RS-485 RTS Driving Level in Auto Direction Mode
The following diagram demonstrates the RS-485 RTS driving level in software control
(RS485_AUD(UA_ALT_CSR[10])=0). The RTS driving level is controlled by programing the
RTS(UA_MCR[1]) control bit.
Setting LEV_RTS(UA_MCR[9]) can control the RTS pin output is inverse or non-inverse from
RTS(UA_MCR[1]) control bit. User can read the RTS_ST(UA_MCR[13]) bit to get real RTS pin
output voltage logic status.
LEV_RTS = 0
LEV_RTS = 1
RTS pin output status of RS-485 function mode (RS-485 AUD mode enabled)
D0
D1
D2
D3
D4
D5
D6
D7
P
Start
bit
Stop
bit
TX pin output*
RTS_ST
(UA_MCR[13]),
RTS pin output
(default)
Driver Enable
Note:
RS485_AUD (UA_ALT_CSR[10]) = 0, support RTS control bit by software control only.
Figure 6.13-18 RS-485 RTS Driving Level with Software Control
Program Sequence Example:
1.
Program FUN_SEL in UA_FUN_SEL to select RS-485 function.
2.
Program the RX_DIS (UA_FCR[8]) to determine enable or disable the receiver RS-485
receiver
3.
Program the RS485_NMM (UA_ALT_CSR[8]) or RS485_AAD (UA_ALT_CSR[9]) mode.
4.
If the RS485_AAD (UA_ALT_CSR[9]) mode is selected, the ADDR_MATCH
(UA_ALT_CSR[31:24]) is programmed for auto address match value.