AN2618

Host interface software

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3

Host interface software

The function partition between the application software and low-level driver is defined during

the software architecture design. To make the software portable, the application software is

normally designed to interface with the low-level driver via abstracted interface APIs. The

host interface of the eTPU functions should be designed such that the implementation of the

low-level driver is hidden from the application software.

Once the application software interface to the low-level driver is defined, the functionality of

the low-level driver can be partitioned between host CPU and eTPU. The eTPU interface

software running on the host CPU is an integral part of the low-level driver. It handles the

details of the interaction between host and eTPU.

The eTPU code and host interface code are compiled by two different compilers. In order to

resolve the eTPU code symbol reference in the host code, it is necessary to export the

symbolic information from the eTPU compiler to the host compiler. Similarly, to build a single

executable image, it is necessary to export eTPU code image to the host compiler. Several

types of information are exported from eTPU_C through host interface files, generated from

#pragma write

statements during compilation. For detailed information on #pragma

write

, see the eTPU_C documentation.

An example of application software and low-level driver partition is shown in Appendix A on

page 11.

3.1

Initialization overview

The eTPU initialization is an important part of the host interface. At the power up, the host

has to configure the eTPU peripheral properly before the eTPU function can be executed.

The eTPU initialization process is accomplished by both host CPU and eTPU. During the

initialization, the functional partition between host CPU and eTPU is as follows:

Host responsibility:

●

eTPU module initialization

●

eTPU channel configuration

●

Providing initial eTPU function parameters

●

Initiating the eTPU function execution

eTPU responsibility:

●

Responding to the HSR

●

Transitioning into the initialization state

The eTPU initialization can be broken down into three steps: eTPU module initialization,

eTPU channel initialization and eTPU function initialization. The following sections discuss

the interface design and the data exchange between host CPU and eTPU for each step of

initialization.

3.2

eTPU module initialization

At the power up initialization, the eTPU peripheral hardware is configured by the host. The

eTPU module initialization includes the following steps: