OXCF950 rev B DATA SHEET V 1.0
OXFORD SEMICONDUCTOR LTD.
external clock options for isochronous applications, e.g.
ISDN, xDSL.
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
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.
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 BETWEENOXCF950 AND OXCF950REV 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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