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MCS7840
USB-2.0 to Four Serial Ports
Page 34
Rev.
1.2
Serial Port (2, 3, & 4) – Device Configuration Register 0
The Configuration Registers for these three Serial Ports are all identical.
They are very similar to Serial Port 1, but have a few less configuration options.
Bit[7]
Bit[6]
Bit[5]
Bit[4]
Bit[3]
Bit[2]
Bit[1]
Bit[0]
Reserved
IrDA_
Mode
RTS_
CM
Reserved
Reserved
RS_
SDM
DCR0
Bit
Name
Definition
Default
Value
0
RS_
SDM
RS-232 / RS-422 / RS-485
Transceiver Shut-Down Mode:
0:
Do not shut down the transceiver
Even when USB SUSPEND is engaged
1:
Shut down the transceiver
when USB SUSPEND is engaged
1
1
Reserved
Reserved
0
[3:2]
Reserved
Reserved
00
[5:4]
RTS_
CM
RTSM RTS Control Method:
00:
RTS is controlled by Control Bit Map.
Signal is active low;
01:
RTS is controlled by Control Bit Map.
Signal is active high;
10:
Drive RTS active
when Downstream Data Buffer is NOT EMPTY;
Otherwise Drive RTS inactive.
11:
Drive RTS inactive
when Downstream Data Buffer is NOT EMPTY;
Otherwise Drive RTS active.
00
6
IrDA_
Mode
0:
RS-232 / RS-422 / RS-485 Serial Port Mode.
1:
IrDA Mode.
0
7
Reserved
Reserved
0
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