Instruction Pipeline Timing Diagram | Motorola MC68340 manual

Freescale Semiconductor, Inc.

Assertion of IPIPE for a single clock cycle indicates the use of data from IRB. Regardless of the presence of valid data in IRA, the contents of IRB are invalidated when IPIPE is asserted. If IRA contains valid data, the data is copied into IRB (IRA ⇒ IRB), and the IRB stage is revalidated.

Assertion of IPIPE for two clock cycles indicates the start of a new instruction and subsequent replacement of data in IRC. This action causes a full advance of the pipeline (IRB ⇒ IRC and IRA ⇒ IRB). IRA is refilled during the next instruction fetch bus cycle.

Data loaded into IRA propagates automatically through subsequent empty pipeline stages. Signals that show the progress of instructions through IRB and IRC are necessary to accurately monitor pipeline operation. These signals are provided by IRA and IRB validity bits. When a pipeline advance occurs, the validity bit of the stage being loaded is set, and the validity bit of the stage supplying the data is negated.

Because instruction execution is not timed to bus activity, IPIPE is synchronized with the system clock, not the bus. Figure 5-29 illustrates the timing in relation to the system clock.

.IR. .

IRB

IRC

IRB

IRC

CLKOUT

IPIPE

EXTENSION	INSTRUCTION	EXTENSION	INSTRUCTION
WORD USED	START	WORD USED	START

Figure 5-29. Instruction Pipeline Timing Diagram

IPIPE should be sampled on the falling edge of the clock. The assertion of IPIPE for a single cycle after one or more cycles of negation indicates use of the data in IRB (advance of IRA into IRB). Assertion for two clock cycles indicates that a new instruction has started (IRB ⇒ IRC and IRA ⇒ IRB transfers have occurred). Loading IRC always indicates that an instruction is beginning execution—the opcode is loaded into IRC by the transfer.

In some cases, instructions using immediate addressing begin executing and initiate a second pipeline advance simultaneously at the same time. IPIPE will not be negated between the two indications, which implies the need for a state machine to track the state of IPIPE. The state machine can be resynchronized during periods of inactivity on the signal.

5.6.3.3OPCODE TRACKING DURING LOOP MODE. IPIPE and IFETCH continue to work normally during loop mode. IFETCH indicates all instruction fetches up through the point that data begins recirculating within the instruction pipeline. IPIPE continues to signal the start of instructions and the use of extension words even though data is being recirculated internally. IFETCH returns to normal operation with the first fetch after exiting loop mode.

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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 Instruction Pipeline Timing Diagram

Models: MC68340

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Figure 5-29. Instruction Pipeline Timing Diagram

MC68340 specifications