gc80c510 CORERIVER Semiconductor, gc80c510 Datasheet - Page 62

• Manufacturer Part Number: gc80c510
• Description: Eprom/rom 8-bit Turbo Microcontrollers
• Manufacturer: CORERIVER Semiconductor

6.2.5 UART (Universal Asynchronous Rx/Tx)
6.2.5.1 Mode 1
communication. 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 register. However any write to SBUF will be to the transmit register, while a read
from SBUF register will be from the receive buffer. The UART port can operate in only Mode 1 as
described below.
10 bits transmitted on TXD and received on RXD. The 10 bits consist of a start bit (0), 8 data bits (LSB
first), and a stop bit (1). On receiving, the stop bit goes into RB8 in the SCON. The baud rate in this
mode is variable. The serial baud rates can be programmed to be 1/16 or 1/32 of the Timer 1 overflow.
Since the Timer 1 can be set to different reload values, a wide variation in baud rates is possible.
[Transmission for UART Communication]
following the first roll-over of divide by 16-bit counter. The next bit is placed on TXD pin at S1 state
following the next roll-over of the divide by 16-bit counter. Thus the transmission is synchronized to the
divide by 16-bit counter and not directly to the write to SBUF signal. After all 8-bit data are transmitted,
the stop bit is transmitted. The TI flag is set in the S1 state after the stop bit has been put out on TXD
pin. This will be at the 10
[Reception for UART Communication]
with the detection of a falling edge on the RXD pin. The 1-to-0 detector continuously monitors the RXD
line, sampling it at the rate of 16 times the selected baud rate. When a falling edge is detected, the
divide by 16-bit counter is immediately reset. This helps to align the bit boundaries with the roll-overs of
the divide by 16-bit counter.
a best of three bases. The bit detector samples the RXD pin, at the 8
using a majority 2 of 3 voting system, the bit value is selected. This is done to improve the noise
rejection feature of the serial port. If the first bit detected after the falling edge of RXD pin is not 0, then
this indicates an invalid start bit, and the reception is immediately aborted. The serial port again looks
for a falling edge in the RXD line. If a valid start bit is detected, then the rest of the bits are also
UART in the MiDAS1.1 family is a full duplex port. The UART ports are capable of asynchronous
In Mode 1, the full duplex asynchronous mode is used. Serial communication frames are made up of
Transmission begins with a write to SBUF. The serial data is brought out on to TXD pin at S1 state
Reception is enabled only if REN is “1”. The UART port actually starts the receiving of serial data,
The 16 states of the counter effectively divide the bit time into 16 slices. The bit detection is done on
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roll-over of the divide by 16-bit counter after a write to SBUF.
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, 9
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, and 10
Functional Description
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counter states. By