AT89C51SND1C-7HTUL Atmel, AT89C51SND1C-7HTUL Datasheet - Page 134

• Manufacturer Part Number: AT89C51SND1C-7HTUL
• Description: IC MCU 64KB FLASH MEM 81-CBGA
• Manufacturer: Atmel
• Series: 89Cr

Specifications of AT89C51SND1C-7HTUL

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: I²C, IDE/ATAPI, MMC, SPI, UART/USART, USB
• Peripherals: Audio, I²S, MP3, PCM, POR, WDT
• Number Of I /o: 44
• Program Memory Size: 64KB (64K x 8)
• Program Memory Type: FLASH
• Ram Size: 2.25K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.3 V
• Data Converters: A/D 2x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 81-CBGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -

18. Serial I/O Port
18.1
18.2
18.2.1
134
Mode Selection
Baud Rate Generator
AT8xC51SND1C
Timer 1
The serial I/O port in the AT8xC51SND1C provides both synchronous and asynchronous com-
munication modes. It operates as a Synchronous Receiver and Transmitter in one single mode
(Mode 0) and operates as an Universal Asynchronous Receiver and Transmitter (UART) in three
full-duplex modes (Modes 1, 2 and 3). Asynchronous modes support framing error detection and
multiprocessor communication with automatic address recognition.
SM0 and SM1 bits in SCON register (see Figure 126) are used to select a mode among the sin-
gle synchronous and the three asynchronous modes according to
Table 124. Serial I/O Port Mode Selection
Depending on the mode and the source selection, the baud rate can be generated from either
the Timer 1 or the Internal Baud Rate Generator. The Timer 1 can be used in Modes 1 and 3
while the Internal Baud Rate Generator can be used in Modes 0, 1
and 3.
The addition of the Internal Baud Rate Generator allows freeing of the Timer 1 for other pur-
poses in the application. It is highly recommended to use the Internal Baud Rate Generator as it
allows higher and more accurate baud rates than Timer 1.
Baud rate formulas depend on the modes selected and are given in the following mode sections.
When using Timer 1, the Baud Rate is derived from the overflow of the timer. As shown in
Figure 18-1 Timer 1 is used in its 8-bit auto-reload mode (detailed in Section "Mode 2 (8-bit
Timer with Auto-Reload)", page 55). SMOD1 bit in PCON register allows doubling of the gener-
ated baud rate.
SM0
0
0
1
1
SM1
0
1
0
1
Mode
0
1
2
3
Description
Synchronous Shift Register
8-bit UART
9-bit UART
9-bit UART
Table
Baud Rate
Fixed/Variable
Variable
Fixed
Variable
124.
4109L–8051–02/08