OXCF950 datasheet(2/66 Pages) OXFORD

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OXCF950 rev B DATA SHEET

OXFORD SEMICONDUCTOR, INC.

The OXCF950 rev B also incorporates a bridge to an 8 bit

Local Bus in Local Bus Mode. It allows card developers to

expand the capabilities of their products by adding

peripherals to this bus. In addition, two user IO pins are

included to enhance external device control. These IO pins

can also be configured as interrupt inputs.

The OXCF950 rev B fixes all known errata of the OXCF950

part. It also adds two new modes of operation. The first

mode (pin or EEPROM selectable) allows the device to

function in embedded systems where the generic device

driver present assumes I/O occupancy of 8 byte

addresses, without any additional components. The second

mode (pin selectable) allows the device to act as a stand-

alone 16C950 type part with the benefits over the 16C950

rev B of 5V tolerance, and packaging options where pin-

compatibility with 550 type UARTs is not required.

SUMMARY OF DIFFERENCES BETWEEN OXCF950 AND OXCF950 REV B

The OXCF950 rev B has been designed to be as compatible as possible with the rev A part. A designer considering switching to

the new device should be aware of the following –

•

Power supply. The new part has a supply voltage range from 2.7V to 3.6V. The original part had a supply voltage

range from 3.15V to 5.25V. A new design requiring operation at both 3.3V and 5V will require an in-line low voltage-

drop regulator.

•

Pin compatible (other than supply voltage constraints).

•

Software compatible – all the modes of the original CF950 are available in the rev B device.

•

All I/Os are now 5V tolerant, with the exception of the Crystal oscillator input.

•

The crystal oscillator circuit is only suitable for frequencies up to 20 MHz. For operation above this frequency, an

external clock source is required.

•

A new ‘generic’ mode has been added allowing generic drivers to access the UART without needing external circuitry

to adjust the address ranges. This mode (8 byte I/O space) can be selected either by pin control or through the

EEPROM. Access to configuration registers is still possible via a software paging technique.

•

A stand-alone 16C950 type mode has been added (pin selectable) to allow the device to be used where pin-

compatibility with 16C550 type devices is not required.

•

All known errata in the original OXCF950 have been fixed.

•

The device is now characterised for an extended operating temperature range of –40C to +105C.

•

The CF950 rev B is additionally available in a 48 TFBGA package.

•

The input clock frequency may be restricted by the CF950 rev B environment. Where an external EEPROM is being

used, the maximum clock frequency of the external EEPROM multiplied by 64 will give a input clock frequency limit.

For an external EEPROM powered off 5V with a maximum frequency of 1MHz, this sets no limits. An EEPROM

powered off 2.7V may typically have a maximum frequency of 250 kHz, which would restrict the CF950 rev B input

frequency to 16 MHz.

Software can identify the difference between an OXCF950 and an OXCF950 rev B by reading the UART REV register (see

6.11.7)

For the original OXCF950 this reads 0x06, for the OXCF950 rev B this reads 0x08.

Throughout this document, the OXCF950 rev B will henceforth simply be referred to as the OXCF950.

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