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DATA COMMUNICATIONS APPLICATION NOTE

DAN183

September 2005

MIGRATING FROM THE XR17D15X TO THE XR17V25X

Author: PY

1.0

INTRODUCTION

This application note describes the changes necessary and what to consider when migrating from the

XR17D15x to the XR17V25x.

2.0

HARDWARE DIFFERENCES

Because the XR17D15x is PCI 2.2 compliant and the XR17V25x is PCI 3.0 compliant, there are some hard-

ware changes to consider when migrating from the XR17D15x to the XR17V25x. In addition, there are some

hardware differences because the XR17V25x has some new and enhanced features. Sections 2.1-2.4 below

lists the hardware differences between the XR17D15x and the XR17V25x.

2.1

VCC/VIO

The VCC and VIO signals were separate on the XR17D15x because the core voltage (VCC) could be operat-

ing at a different voltage than the I/O voltage (VIO). For an add-in card example, VCC could be at 5V while

VIO could be either 3.3V or 5V depending on whether it was plugged into a 3.3V slot or a 5V slot. There are no

separate VIO and VCC signals for the XR17V25x because it is a 3.3V only PCI UART. The XR17V25x is 3.3V

only because there are no 5V specifications in PCI 3.0.

2.2

The XR17D15x can operate with a PCI clock of up to 33 MHz while the XR17V25x can operate with a PCI

clock of up to 66 MHz. To operate at 66 MHz, the M66EN signal on the PCI bus should be connected to VCC.

2.3

The XR17V25x operates at a faster data rate than the XR17D15x. With an 8X sampling rate, the XR17V25x

can operate up to more than 8Mbps while the XR17D15x could only operate up to 6.25Mbps.

XR17D15x

3.3V or 5V

3.3V or 5V

XR17V25x

3.3V Only

3.3V Only

XR17D15x

33 MHz

XR17V25x

66 MHz

XR17D15x

50 MHz

6.25 Mbps

XR17V25x

66 MHz

8.25 Mbps