W77E058A40PL Nuvoton Technology Corporation of America, W77E058A40PL Datasheet - Page 63

• Manufacturer Part Number: W77E058A40PL
• Description: IC MCU 8-BIT 32K FLASH 44-PLCC
• Manufacturer: Nuvoton Technology Corporation of America
• Series: W77r

Specifications of W77E058A40PL

• Program Memory Type: FLASH
• Program Memory Size: 32KB (32K x 8)
• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: EBI/EMI, Serial Port
• Peripherals: POR, WDT
• Number Of I /o: 36
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 44-PLCC
• Cpu Family: W77
• Device Core: 8051
• Device Core Size: 8b
• Frequency (max): 40MHz
• Interface Type: UART
• Total Internal Ram Size: 1KB
• # I/os (max): 32
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 4.5V
• Instruction Set Architecture: CISC
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 44
• Package Type: PLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Data Converters: -
• Lead Free Status / RoHS Status: Compliant, Lead free / RoHS Compliant

W77E058A
14. SERIAL PORT
Serial port in the W77E058 is a full duplex port. The W77E058 provides the user with additional
features such as the Frame Error Detection and the Automatic Address Recognition. The serial ports
are capable of synchronous as well as asynchronous communication. In Synchronous mode the
W77E058 generates the clock and operates in a half duplex mode. In the asynchronous mode, full
duplex operation is available. This means that it can simultaneously transmit and receive data. The
transmit register and the receive buffer are both addressed as SBUF Special Function Register.
However any write to SBUF will be to the transmit register, while a read from SBUF will be from the
receive buffer register. The serial port can operate in four different modes as described below.
14.1 Mode 0
This mode provides synchronous communication with external devices. In this mode serial data is
transmitted and received on the RXD line. TXD is used to transmit the shift clock. The TxD clock is
provided by the W77E058 whether the device is transmitting or receiving. This mode is therefore a half
duplex mode of serial communication. In this mode, 8 bits are transmitted or received per frame. The
LSB is transmitted/received first. The baud rate is fixed at 1/12 or 1/4 of the oscillator frequency. This
baud rate is determined by the SM2 bit (SCON.5). When this bit is set to 0, then the serial port runs at
1/12 of the clock. When set to 1, the serial port runs at 1/4 of the clock. This additional facility of
programmable baud rate in mode 0 is the only difference between the standard 8051 and the
W77E058.
The functional block diagram is shown below. Data enters and leaves the Serial port on the RxD line.
The TxD line is used to output the shift clock. The shift clock is used to shift data into and out of the
W77E058 and the device at the other end of the line. Any instruction that causes a write to SBUF will
start the transmission. The shift clock will be activated and data will be shifted out on the RxD pin till all
8 bits are transmitted. If SM2 = 1, then the data on RxD will appear 1 clock period before the falling
edge of shift clock on TxD. The clock on TxD then remains low for 2 clock periods, and then goes high
again. If SM2 = 0, the data on RxD will appear 3 clock periods before the falling edge of shift clock on
TxD. The clock on TxD then remains low for 6 clock periods, and then goes high again. This ensures
that at the receiving end the data on RxD line can either be clocked on the rising edge of the shift clock
on TxD or latched when the TxD clock is low.
Publication Release Date: April 17, 2007
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Revision A10