JTAG/Debug Port

9

9.1Description

The JTAG/Debug port is essentially several shift registers, with the destination controlled by the TMS pin and data I/O with TDI/TDO. nTRST provides initialization of the test logic. JTAG is testable via the IEEE 1149.1. Many use JTAG to control the address/data bus for Flash programming. JTAG is also a hardware debug port.

9.2Schematics

All JTAG pins, except for nTRST and TCK, are directly connected. TCK is not driven internally and so you must add an external pull-up or pull-down resistor. Intel recommends adding a 1.5 k pull-down resistor to TCK. nTRST must be asserted during power-on. Asserting nRESET or nTRST must not cause the other reset signal to assert. Also, use an external pull-up resistor on nTRST to prevent spurious resets of the JTAG port when disconnected. The circuit in Figure 9-1drives nTRST. It uses a reset IC on nTRST to ensure that nTRST is reset at power-on. nRESET must be directly connected to the CPU nRESET. Do not connect pins 17 and 19 – they are special purpose functions and not used.

Figure 9-1. JTAG/Debug Port Wiring Diagram

3.3 V

 

RESET

MR

 

1

2

nTRST

 

3

4

MAX823

 

 

TDI

5

6

 

 

 

 

 

 

TMS

7

8

 

TCK

 

9

10

 

 

1.5K

GND

11

12

 

 

 

TDO

13

14

nRESET

 

 

 

15

16

 

 

 

 

17

18

 

 

 

 

19

20

If you are not utilizing either JTAG or the hardware debug functions, it is highly recommended that you design in a JTAG/debug port on your system anyway. This greatly facilitates board debug, startup, and software development. During final production you would not have to populate the JTAG connector.

PXA250 and PXA210 Applications Processors Design Guide

9-1

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Intel PXA250 and PXA210 manual JTAG/Debug Port, Description

PXA250 and PXA210 specifications

The Intel PXA250 and PXA210 processors, part of the Intel XScale architecture, were introduced in the early 2000s, targeting mobile and embedded applications. They are known for their low power consumption, high performance, and advanced multimedia capabilities, making them suitable for a wide range of devices, including PDAs, smartphones, and other portable computing devices.

The PXA250, which operates at clock speeds ranging from 400 MHz to 624 MHz, features a superscalar architecture that allows it to issue multiple instructions per clock cycle. This enhances the overall performance for demanding applications while maintaining low power usage. It supports a variety of peripheral interfaces, including USB, Ethernet, and various memory types, which contributes to its versatility in different product designs.

One of the key technologies in the PXA250 is the integrated Intel Smart Repeat Technology, which optimizes data processing, thereby reducing the amount of power consumed during operation. This feature is particularly important for battery-powered devices, as it extends the overall battery life, allowing for longer usage times in mobile environments. Additionally, the PXA250 includes a dedicated graphics acceleration unit, which enables enhanced graphics and multimedia performance suited to modern applications at the time.

In contrast, the PXA210 is a more entry-level processor, aimed at cost-sensitive applications. Operating at lower clock speeds, typically around 200 MHz to 400 MHz, it forgoes some of the advanced performance features of the PXA250 while still offering a good balance of performance and power efficiency. The PXA210 is less complex, making it suitable for simpler devices that do not require the extensive capabilities of the PXA250.

Both processors utilize the Intel XScale architecture, which is based on the ARM instruction set. They are built on a 0.13-micron process technology, enabling higher density and lower power consumption compared to their predecessors. With integrated memory controllers and bus interfaces, they facilitate efficient data handling and connectivity options.

In summary, both the Intel PXA250 and PXA210 processors played a crucial role in the evolution of mobile computing by providing powerful processing capabilities with energy efficiency. Their features and technologies enabled device manufacturers to create innovative products that catered to the growing demand for portable devices during that era.