TAP Controller, Test Access Port Block Diagram

Freescale Semiconductor, Inc.

An overview of the MC68340 implementation of IEEE 1149.1 is shown in Figure 9-1. The MC68340 implementation includes a 16-state controller, a 3-bit instruction register, and two test registers (a 1-bit bypass register and a 132-bit boundary scan register). This implementation includes a dedicated TAP consisting of the following signals:

TCK — a test clock input to synchronize the test logic

TMS — a test mode select input (with an internal pullup resistor) that is sampled on the rising edge of TCK to sequence the TAP controller's state machine

TDI — a test data input (with an internal pullup resistor) that is sampled on the rising edge of TCK.

TDO — a three-state test data output that is actively driven in the shift-IR and shift-

DR controller states. TDO changes on the falling edge of TCK.

Freescale Semiconductor, Inc.

	TEST DATA REGISTERS
	132	0
	BOUNDARY SCAN REGISTER
	(133 BITS)
TDI
	BYPASS
	DECODER
	2	0
	3-BIT INSTRUCTION REGISTER
TMS
TCK	TAP
	CTLR

M U X

TDO

Figure 9-1. Test Access Port Block Diagram

9.2 TAP CONTROLLER

The TAP controller is responsible for interpreting the sequence of logical values on the TMS signal. It is a synchronous state machine that controls the operation of the JTAG logic. The state machine is shown in Figure 9-2; the value shown adjacent to each arc represents the value of the TMS signal sampled on the rising edge of the TCK signal. For a description of the TAP controller states, please refer to the IEEE 1149.1 document.

9- 2MC68340 USER’S MANUALMOTOROLA

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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 TAP Controller, Test Access Port Block Diagram

Models: MC68340

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Figure 9-1. Test Access Port Block Diagram

9.2 TAP CONTROLLER

MC68340 specifications