Registers – Rainbow Electronics T89C5115 User Manual
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45
T89C5115
4128A–8051–04/02
For slaves A and B, bit 2 is a don’t care bit; for slave C, bit 2 is set. To communicate with
all of the slaves, the master must send an address FFh. To communicate with slaves A
and B, but not slave C, the master can send and address FBh.
Registers
Table 26. SCON Register
SCON (S:98h)
Serial Control Register
Reset Value = 0000 0000b
Bit addressable
7
6
5
4
3
2
1
0
FE/SM0
SM1
SM2
REN
TB8
RB8
TI
RI
Bit
Number
Bit
Mnemonic
Description
7
FE
Framing Error bit (SMOD0 = 1)
Clear to reset the error state, not cleared by a valid stop bit.
Set by hardware when an invalid stop bit is detected.
–
SM0
Serial port Mode bit 0 (SMOD0 = 0)
Refer to SM1 for serial port mode selection.
6
SM1
Serial port Mode bit 1
SM0 SM1
Mode
Baud Rate
0
0
Shift Register F
XTAL
/12 (or F
XTAL
/6 in mode X2)
0
1
8-bit UART
Variable
1
0
9-bit UART
F
XTAL
/64 or F
XTAL
/32
1
1
9-bit UART
Variable
5
SM2
Serial port Mode 2 bit/Multiprocessor Communication Enable bit
Clear to disable multiprocessor communication feature.
Set to enable multiprocessor communication feature in mode 2 and 3.
4
REN
Reception Enable bit
Clear to disable serial reception.
Set to enable serial reception.
3
TB8
Transmitter Bit 8/Ninth bit to transmit in modes 2 and 3
Clear to transmit a logic 0 in the 9th bit.
Set to transmit a logic 1 in the 9th bit.
2
RB8
Receiver Bit 8/Ninth bit received in modes 2 and 3
Cleared by hardware if 9th bit received is a logic 0.
Set by hardware if 9th bit received is a logic 1.
1
TI
Transmit Interrupt flag
Clear to acknowledge interrupt.
Set by hardware at the end of the 8th bit time in mode 0 or at the beginning of the
stop bit in the other modes.
0
RI
Receive Interrupt flag
Clear to acknowledge interrupt.
Set by hardware at the end of the 8th bit time in mode 0, see Figure 20 and
Figure 21 in the other modes.