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Freescale Semiconductor, Inc.

ARCHIVED BY FREESCALE SEMICONDUCTOR, INC. 2005

Freescale Semiconductor, Inc.

JTAG Port

ARCHIVED BY FREESCALE SEMICONDUCTOR, INC. 2005

13.1 JTAG/OnCE Port Pinout

As described in IEEE 1149.1a-1993, the JTAG port requires a minimum of four pins to support TDI, TDO, TCK, and TMS signals. The DSP56824 also uses the optional TRST input signal and multiplexes it so that the same pin can support the debug event (DE) output signal used by the OnCE module interface. The pin functions are described in Table 13-1.

 

 

 

 

 

 

 

 

 

Table 13-1. JTAG Pin Descriptions

 

 

 

 

 

 

 

 

 

Pin Name

 

 

 

 

 

 

 

Pin Description

 

 

 

 

 

 

 

TDI

Test Data Input— This input pin provides a serial input data stream to the JTAG and the OnCE

 

 

 

 

 

module. It is sampled on the rising edge of TCK and has an on-chip pull-up resistor.

 

 

 

 

 

 

 

TDO

Test Data Output— This tri-statable output pin provides a serial output data stream from the

 

 

 

 

 

JTAG and the OnCE module. It is driven in the Shift-IR and Shift-DR controller states of the

 

 

 

 

 

JTAG state machine and changes on the falling edge of TCK.

 

 

 

 

 

 

 

TCK

Test Clock Input— This input pin proves a gated clock to synchronize the test logic and shift

 

 

 

 

 

serial data to and from the JTAG/OnCE port. If the OnCE module is not being accessed, the

 

 

 

 

 

maximum TCK frequency is as specified in the DSP56824 Technical Data. When accessing the

 

 

 

 

 

OnCE module through the JTAG TAP, the maximum frequency for TCK is one-eighth the maxi-

 

 

 

 

 

mum frequency specified for the DSP56824 core (that is, 8.75 MHz for TCK if the maximum CLK

 

 

 

 

 

input is 70 MHz).

 

 

 

 

 

The TCK pin has an on-chip pull-down resistor.

 

 

 

 

 

 

 

TMS

Test Mode Select Input— This input pin is used to sequence the JTAG TAP controller’s state

 

 

 

 

 

machine. It is sampled on the rising edge of TCK and has an on-chip pull-up resistor.

 

 

 

 

 

 

 

 

 

 

 

/

 

 

Test Reset/Debug Event— This bidirectional pin, when configured as an input, provides a reset

 

TRST

DE

 

 

 

 

 

signal to the JTAG TAP controller. When configured as an output, it signals debug events

 

 

 

 

 

detected on a trigger condition. The operational mode of the pin is configured by bit 14 of the

 

 

 

 

 

OnCE control register (OCR).

 

 

 

 

 

The

 

/

 

pin has an on-chip pull-up resistor.

 

 

 

 

 

TRST

DE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: Implementation of the TRST/DE pin is not fully compliant with IEEE 1149.1a-1993.

13.2 JTAG Port Architecture

The TAP controller is a simple state machine used to sequence the JTAG port through its valid operations, including the following:

Serially shifting in or out a JTAG port command

Updating (and decoding) the JTAG port instruction register (IR)

Serially inputting or outputting a data value

Updating a JTAG port (or OnCE module) register

NOTE:

The JTAG port oversees the shifting of data into and out of the OnCE module through the TDI and TDO pins, respectively. In this case, the shifting is guided by the same TAP controller used when shifting JTAG information.

13-2 DSP56824 User’s Manual

For More Information On This Product,

Go to: www.freescale.com

Freescale Semiconductor, Inc.

ARCHIVED BY FREESCALE SEMICONDUCTOR, INC. 2005

Freescale Semiconductor, Inc.JTAG Port Architecture

ARCHIVED BY FREESCALE SEMICONDUCTOR, INC. 2005

 

To OnCE Port

TDI

Instruction Register

 

Decode

 

TDO

 

Boundary Scan Register

 

ID Register

 

Bypass Register

TMS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

From OnCE Port

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TAP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TCK

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Controller

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TRST

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

AA1393

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 13-1. JTAG Block Diagram

 

A block diagram of the JTAG port is shown in Figure 13-1. The JTAG port has four read/write registers: the IR, BSR, device identification register, and bypass register. Access to the OnCE registers is described in Chapter 12, “OnCE™ Module.”

The TAP controller provides access to the JTAG IR through the JTAG port. The other JTAG registers must be individually selected by the JTAG IR. Figure 13-2 shows the programming models for the JTAG registers on the DSP56824.

JTAG Port 13-3

For More Information On This Product,

Go to: www.freescale.com

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