TCx Control Bits | Motorola MC68340 guide

Freescale Semiconductor, Inc.

Start Break—The start break command forces the channel's TxDx low. If the transmitter is empty, the start of the break conditions can be delayed up to one bit time. If the transmitter is active, the break begins when transmission of the character is complete. If a character is in the transmitter shift register, the start of the break is delayed until the character is transmitted. If the transmitter holding register has a character, that character is transmitted after the break. The transmitter must be enabled for this command to be accepted. The state of the CTS≈ input is ignored for this command.

Stop Break—The stop break command causes the channel's TxDx to go high (mark) within two bit times. Characters stored in the transmitter buffer, if any, are transmitted.

Assert RTS—The assert RTS command forces the channel'sRTS≈ output low.

Negate RTS—The negate RTS command forces the channel'sRTS≈ output high.

TC1–TC0—Transmitter Commands

These bits select a single command as listed in Table 7-7.

Table 7-7. TCx Control Bits

TC1	TC0	Command
0	0	No Action Taken
0	1	Enable Transmitter
1	0	Disable Transmitter
1	1	Do Not Use

No Action Taken—The no action taken command causes the transmitter to stay in its current mode. If the transmitter is enabled, it remains enabled; if disabled, it remains disabled.

Transmitter Enable—The transmitter enable command enables operation of the channel's transmitter. The TxEMP and TxRDY bits in the SR are also set. If the transmitter is already enabled, this command has no effect.

Transmitter Disable—The transmitter disable command terminates transmitter operation and clears the TxEMP and TxRDY bits in the SR. However, if a character is being transmitted when the transmitter is disabled, the transmission of the character is completed before the transmitter becomes inactive. If the transmitter is already disabled, this command has no effect.

Do Not Use—Do not use this bit combination because the result is indeterminate.

MOTOROLAMC68340 USER’S MANUAL7- 29

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MC68340 specifications

The Motorola MC68340 is a highly integrated microprocessor that was introduced in the early 1990s. It belongs to the 68000 family of microprocessors and is designed to cater to the demands of embedded systems, particularly in telecommunications and networking applications. This chip represents a significant evolution in microprocessor technology by combining a microprocessor core with additional peripherals on a single chip, making it an attractive solution for engineers looking to design compact and efficient systems.

One of the key features of the MC68340 is its 32-bit architecture, which allows for significant processing power and data handling capabilities. This architecture enables the processor to handle larger data sizes and perform more complex calculations compared to its 16-bit predecessors. The MC68340 operates at clock speeds typically ranging from 16 MHz to 25 MHz. Its dual instruction pipeline enhances throughput, allowing for simultaneous instruction fetches and executions, which significantly boosts performance.

A notable characteristic of the MC68340 is the inclusion of integrated peripherals, which help reduce the overall component count in a system. Key integrated components include a memory management unit (MMU), a direct memory access (DMA) controller, and various communication interfaces such as serial ports. The memory management capabilities enhance the processor's ability to manage memory resources efficiently, enabling it to support multitasking environments commonly found in modern computing.

In terms of connectivity, the MC68340 features connections for both synchronous and asynchronous serial communication, making it well-suited for networking tasks. The processor supports a range of bus standards, including address and data buses, which facilitate seamless interaction with peripheral devices.

Another important aspect of the MC68340 is its flexibility. The processor supports multiple operating modes, including multiple CPU configurations and compatibility with the Motorola 68000 family, allowing for easier integration into existing systems.

Moreover, the MC68340 boasts low power consumption compared to many of its contemporaries, making it an excellent choice for battery-operated applications, enhancing its appeal in sectors like telecommunications, industrial control, and automotive systems. Its combination of performance, integration, versatility, and efficiency has secured the MC68340 a reputable position in the annals of embedded systems technology, proving to be a valuable asset for developers and engineers alike.

Motorola MC68340 manual TCx Control Bits

Models: MC68340

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Table 7-7. TCx Control Bits

MOTOROLAMC68340 USER’S MANUAL7- 29

MC68340 specifications