TransDimension Inc.
Interfacing OTG243 to Motorola MCF5272 ColdFire Processor
2. Bus Interface
2.1
Recommendations
For the MCF5272, we recommend that:
The OTG243 is interfaced directly to MCF5272’s system bus.
The OTG243 operates in 16-bit mode (pin
/EXVBO
pulled-down). This reference design has
been tested in 16-bit mode, but should work just as well in 32-bit mode.
The OTG243 is accessed through the MCF5272 chip-select as memory-mapped peripheral.
Any of the chip-select signals
nCS[5:2]
can be programmed for an address location, with
masking capabilities, port size, burst capability indication, and wait-state generation.
nCS2
is used for this reference design.
The chosen chip-select is programmed to 16-bit access with a bus cycle compatible to that of
the OTG243’s.
The above recommendations are assumed throughout this document. Alternative interfacing
schemes, such as 32-bit access to the OTG243, can function just as well.
2.2
Required Procedure
MCF5272 operates under big endian mode, but OTG243 operates under the little endian mode.
Software is required to perform byte swapping for the data.
2.3
Hardware Design
This sub-section discusses hardware aspects of interfacing the OTG243 to the MCF5272.
Software considerations are presented in Section 2.3.
The following signals of the OTG243 are involved in the bus interfacing. For simplicity and
clarity, buffers are not inserted between the MCF5272 and the OTG243. One should use his/her
own judgment on this issue based on a specific application.
Operating Mode: /EXVBO and
TEST
/EXVBO
should be pulled down for 16-bit operation, and the
TEST
pin must be grounded.
3
OXFORD [ OXFORD SEMICONDUCTOR ]
