Hardware Description

the JTAG signals are routed through the ARM926EJ-S PXP Development Chip

a debugger, RealView Debugger for example, controls the scan chain

The PLDs and FPGAs are not visible on the scan chain unless they contain debuggable devices

If RealView Logic Tiles are present and have debuggable devices, the D_x signals are part of their JTAG scan chain

the FPGAs in the system load their images from configuration flash.

JTAG configuration mode

This mode is selected if the CONFIG link is fitted (see Figure 3-42 on page 3-95).

Note

The CONFIG link has been replaced by a switch on some board versions. The switch must be in the ON position to select JTAG configuration mode.

In configuration mode:

The signal nCFGEN is low.

The CONFIG LED is lit on the PB926EJ-S (and on each tile in the stack).

The JTAG scan path is rerouted to include configurable devices.

A configuration utility, ProgCards for example, controls the scan chain.

If RealView Logic Tiles are present, the C_x signals are part of the JTAG scan chain.

All FPGAs and PLDs in the system (including any devices in a RealView Logic Tile) are added into the scan chain.

The TAP controller in the ARM926EJ-S PXP Development Chip is not visible and is replaced by a Boundary Scan TAP controller that is used for board-level production testing.

This enables the board to be configured or upgraded in the field using JTAG equipment or the onboard USB debug port.

The nonvolatile PLDs devices can be reprogrammed directly by JTAG.

FPGA images can be loaded from the scan chain.

ARM DUI 0224I

Copyright © 2003-2010 ARM Limited. All rights reserved.

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ARM ARM DUI 0224I manual Jtag configuration mode