AT89C51RE2 Atmel Corporation, AT89C51RE2 Datasheet - Page 100

• 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

Internal Baud Rate
Generator (BRG)
Figure 42. Internal Baud Rate generator 0
Figure 43. Internal Baud Rate generator 1
100
AT89C51RE2
BRR_1
BRR_0
F
F
PER
PER
The AT89C51RE2 implements two internal baudrate generators. Each one is dedicated to the
corresponding UART. The configuration and operating mode for both BRG are similar. When an
internal Baud Rate Generator is used, the Baud Rates are determined by the BRG overflow
depending on the BRL (BRL or BRL_1 registers) reload value, the value of SPD (or SPD_1) bit
(Speed Mode) in BDRCON (BDRCON_1) register and the value of the SMOD1 bit in PCON
register.
•
Baud_Rate =
BRL = 256 -
The baud rate for UART is token by formula:
6
6
(1-SPD)
(1-SPD)
/6
/6
2
2
SMOD1
SMOD1
⋅ 32 ⋅ Baud_Rate
⋅ 32 ⋅ (256 -BRL)
⋅ F
⋅ F
SPD_0
PER
PER
SPD_1
0
0
1
1
auto reload counter
auto reload counter
BRL_0
BRL_1
BRG
BRG
overflow
overflow
/2
/2
SMOD1
SMOD1_1
0
0
1
1
INT_BRG
INT_BRG1
7663E–8051–10/08