-USART. Serial I/O – Programmable Communication Interface. Data Communications. Data communications refers to the ability of one computer to. USART The is a USART (Universal Synchronous Asynchronous Receiver Transmitter) for serial data communication. Interrupt Structure of . The modem control unit handles the modem handshake signals to coordinate the communication between modem and transmit control unit.
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The terminal controls data transmission if the device is set in “TX Enable” status by a command. Unless the CPU reads a data character before the next one is received completely, the preceding data will be lost.
The bit configuration of status word is shown in Fig. This is a terminal which indicates that the contains a character that is ready to READ.
As the transmitter is disabled by setting CTS “High” or command, data written before disable will be sent out. Command is used for setting the operation of the That adchitecture, the writing of a control word after resetting will be recognized as a “mode instruction. This is the “active low” input terminal which selects the at low level when the CPU accesses.
This is an output terminal for transmitting data from which serial-converted data is sent out. Table 1 shows the operation between a CPU and the device.
This is the “active low” input terminal which receives a signal for writing transmit data and control words from the CPU into the This device also receives serial data from the outside and transmits parallel arxhitecture to the CPU after conversion.
This is an input terminal which receives a signal architefture selecting data or command words and status words when the is accessed by the CPU. This is a clock input signal which determines the transfer speed of transmitted data.
It is possible to see the internal status of the by reading a status word. This is an output terminal which indicates that the has transmitted all the characters and had no data character. The bit configuration of mode instruction is shown in Figures 2 and 3. In “synchronous mode,” the baud rate is the same as the frequency of RXC.
This architectrue the “active low” input terminal which receives a signal for reading receive data and status words from the Mode instruction is used for setting the function of the The functional configuration is programed by software.
In architeccture synchronous mode. Mode instruction will be in “wait for write” at either internal reset or external reset. In “asynchronous mode”, it is possible to select architdcture baud rate factor by mode arcgitecture. In the case of synchronous mode, it is necessary to write one-or two byte sync characters.
If sync characters were written, a function will be set because the writing of sync characters constitutes part of mode instruction. This is an output terminal which indicates that the is ready to accept a transmitted data character.
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Even if a data is written after disable, that data is not sent out and TXE will be “High”. Architectue the transmitter is enabled, it sent out.
It is also usrt to set the device in “break status” low level by a command. If a status word is read, the terminal will be reset. In “synchronous mode,” the baud rate will be the same as the frequency of TXC. After Reset is active, the terminal will be output at low level.
In “asynchronous mode,” this is an output terminal which generates “high level”output upon the detection of a “break” character if receiver data contains a “low-level” space between the stop bits of two continuous characters.
In “external synchronous mode, “this is an input terminal. It is possible to set the status of DTR by a command. In such a case, an overrun error flag status word will be set.
In “synchronous mode,” the terminal is at high level, if transmit data characters are no longer remaining and sync characters are automatically transmitted. It is possible to set the status RTS by a command.
A “High” on this input forces the to start receiving data characters. The input status of architecturre terminal can be recognized by the CPU reading status words. As a peripheral device of a microcomputer system, the receives parallel data from the CPU and transmits serial data after conversion.
UNIVERSAL SYNCHRONOUS ASYNCHRONOUS RECEIVER TRANSMITTER
The device is in “mark status” high level after resetting or during a status when transmit is disabled. Data is transmitable if the terminal is at low level. CLK signal is used to generate internal device timing.
In “asynchronous mode,” it is possible to select the baud rate factor by mode instruction. The falling edge of TXC sifts the serial data out of the It is possible to write a command whenever necessary after writing a mode instruction and sync characters.
This is a terminal whose function changes according to mode.