Bypass X1X, Hi-Z, MC68340 Restrictions

Inc.

Freescale Semiconductor, Inc.

NOTE

Since there is no internal synchronization between the IEEE 1149.1 clock (TCK) and the system clock (CLKOUT), the user must provide some form of external synchronization to achieve meaningful results.

The second function of SAMPLE/PRELOAD is to initialize the boundary scan register output bits prior to selection of EXTEST. This initialization ensures that known data will appear on the outputs when entering the EXTEST instruction.

9.4.3 BYPASS (X1X, 101)

The BYPASS instruction selects the single-bit bypass register as shown in Figure 9-9. This creates a shift-register path from TDI to the bypass register and, finally, to TDO, circumventing the 132-bit boundary scan register. This instruction is used to enhance test efficiency when a component other than the MC68340 becomes the device under test.

Semiconductor,

SHIFT DR	G1

0	1
	MUX
FROM TDI	1

1 D

CLOCK DR

TO TDO

Freescale

Figure 9-9. Bypass Register

When the bypass register is selected by the current instruction, the shift-register stage is set to a logic zero on the rising edge of TCK in the capture-DR controller state. Therefore, the first bit to be shifted out after selecting the bypass register will always be a logic zero.

9.4.4 HI-Z (100)

The HI-Z instruction is not included in the IEEE 1149.1 standard. It is provided as a manufacturer’s optional public instruction to prevent having to backdrive the output pins during circuit-board testing. When HI-Z is invoked, all output drivers, including the two- state drivers, are turned off (i.e., high impedance). The instruction selects the bypass register.

9.5 MC68340 RESTRICTIONS

The control afforded by the output enable signals using the boundary scan register and the EXTEST instruction requires a compatible circuit-board test environment to avoid device-destructive configurations. The user must avoid situations in which the MC68340 output drivers are enabled into actively driven networks. Overdriving the TDO driver when it is active is not recommended.

MOTOROLAMC68340 USER’S MANUAL9- 11

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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 manual Bypass X1X, Hi-Z, MC68340 Restrictions

Models: MC68340