AT89C51RE2 Atmel Corporation, AT89C51RE2 Datasheet - Page 102

• Manufacturer Part Number: AT89C51RE2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RE2

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Spi: 1
• Uart: 2
• Sram (kbytes): 8.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART/OCD
• Watchdog: Yes

102
AT89C51RE2
Table 69. SCON_1 Register
SCON_1 - Serial Control Register for UART 1(C0h)
Reset Value = 0000 0000b
Bit addressable
FE/SM0_1
Number
7
Bit
7
6
5
4
3
2
1
0
SM1_1
6
Mnemonic
SM0_1
SM1_1
SM2_1
REN_1
RB8_1
TB8_1
FE_1
RI_1
TI_1
Bit
SM2_1
5
Description
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.
SMOD0_1 must be set to enable access to the FE_1 bit.
Serial port Mode bit 0
Refer to SM1_1 for serial port mode selection.
SMOD0_1 must be cleared to enable access to the SM0_1 bit.
Serial port Mode bit 1
SM0
0
0
1
1
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, and
eventually mode 1.This bit should be cleared in mode 0.
Reception Enable bit
Clear to disable serial reception.
Set to enable serial reception.
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.
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.
In mode 1, if SM2_1 = 0, RB8 is the received stop bit. In mode 0 RB8 is not used.
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.
Receive Interrupt flag
Clear to acknowledge interrupt.
Set by hardware at the end of the 8th bit time in mode 0, see Figure 38. and
Figure 39. in the other modes.
SM1
0
1
0
1
REN_1
4
Mode Description
0
1
2
3
Shift Register
8-bit UART
9-bit UART
9-bit UART
TB8_1
3
Baud Rate
F
Variable
F
Variable
CPU PERIPH
CPU PERIPH
RB8_1
2
/6
/32 or /16
TI_1
1
7663E–8051–10/08
RI_1
0