Table C-9. SCON1 Register - SFR C0h
Bit
Function
SCON1.7
SCON1.6
SM0_1 - Serial Port 1 mode bit 0.
SM1_1 - Serial Port 1 mode bit 1, decoded as:
SM0_1
SM1_1
Mode
0
0
1
1
0
1
0
1
0
1
2
3
SCON1.5
SM2_1 - Multiprocessor communication enable. In modes 2
and 3, this bit enables the multiprocessor communication
feature. If SM2_1 = 1 in mode 2 or 3, then RI_1 will not be
activated if the received 9th bit is 0.
If SM2_1=1 in mode 1, then RI_1 will only be activated if a
valid stop is received. In mode 0, SM2_1 establishes the
baud rate: when SM2_1=0, the baud rate is CLK24/12; when
SM2_1=1, the baud rate is CLK24/4.
SCON1.4
SCON1.3
SCON1.2
REN_1 - Receive enable. When REN_1=1, reception is
enabled.
TB8_1 - Defines the state of the 9th data bit transmitted in
modes 2 and 3.
RB8_1 - In modes 2 and 3, RB8_0 indicates the state of the
9th bit received. In mode 1, RB8_1 indicates the state of the
received stop bit. In mode 0, RB8_1 is not used.
SCON1.1
SCON1.0
TI_1 - Transmit interrupt flag. indicates that the transmit data
word has been shifted out. In mode 0, TI_1 is set at the end
of the 8th data bit. In all other modes, TI_1 is set when the
stop bit is placed on the TXD0 pin. TI_1 must be cleared by
the software.
RI_1 - Receive interrupt flag. Indicates that serial data word
has been received. In mode 0, RI_1 is set at the end of the 8th
data bit. In mode 1, RI_1 is set after the last sample of the
incoming stop bit, subject to the state of SM2_1. In modes 2
and 3, RI_1 is set at the end of the last sample of RB8_1.
RI_1 must be cleared by the software.
C - 16
Appendix C: 8051 Hardware Description
EZ-USB TRM v1.9
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