AT89C51AC3 Atmel Corporation, AT89C51AC3 Datasheet - Page 8

• Manufacturer Part Number: AT89C51AC3
• Manufacturer: Atmel Corporation

Specifications of AT89C51AC3

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 62.5
• Sram (kbytes): 2.25
• Eeprom (bytes): 2048
• Self Program Memory: API
• Operating Voltage (vcc): 3.0 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

Protocol
Overview
Communication
Initialization
Autobaud
Performances
8
AT89C51AC3 UART Bootloader
An initialization step must be performed after each Reset. After microcontroller reset, the boot-
loader waits for an autobaud sequence (see Section “Autobaud Performances”).
When the communication is initialized the protocol depends on the record type issued by the
host.
The host initiates the communication by sending a ’U’ character to help the bootloader to com-
pute the baud rate (autobaud).
Figure 2. Initialization
The bootloader supports a wide range of baud rates. It is also adaptable to a wide range of oscil-
lator frequencies. This is accomplished by measuring the bit-time of a single bit in a received
character. This information is then used to program the baud rate in terms of timer counts based
on the oscillator frequency. Table 2 shows the autobaud capabilities.
Table 2. Autobaud Performances
Frequency
(MHz)
Baudrate
(kHz)
2400
4800
9600
19200
38400
57600
115200
Frequency
(MHz)
Baudrate
(kHz)
2400
4800
9600
19200
Communication Opened
Init Communication
Else
If (not received "U")
1.8432
Host
OK
OK
OK
OK
OK
OK
OK
OK
8
-
-
-
OK
10
OK
OK
OK
OK
2
-
-
-
-
-
-
11.0592
2.4576
OK
OK
OK
OK
OK
OK
OK
OK
OK
-
-
12
OK
OK
OK
OK
OK
OK
OK
OK
3
-
-
"U"
3.6864
14.746
"U"
OK
OK
OK
OK
OK
OK
OK
OK
OK
OK
-
OK
OK
OK
16
OK
OK
OK
OK
4
-
-
-
-
Sends Back ‘U’ Character
Performs Autobaud
OK
OK
OK
OK
20
OK
OK
OK
OK
5
-
-
-
Bootloader
OK
OK
OK
OK
OK
24
OK
OK
OK
OK
6
-
-
4386B–8051–03/08
7.3728
26.6
OK
OK
OK
OK
OK
OK
OK
OK
OK
OK
OK