Manual

Chapter 11. Porting Guide
The problem also occurred on any targets with multiple serial ports where the ROM monitor was configured to
use a different port than the CDL defaults.
• Proper control of when to mangle or just write out raw ASCII text.
Sometimes it’s desirable to disable mangling, even if the channel specified is the same as that used for debugging.
This usually happens if GDB is used to download the application, but direct interaction with the application on
the same channel is desired (GDB protocol only allows output from the target, no input).
The calling Interface API
The calling interface API is defined by hal_if.h and hal_if.c in hal/common.
The API provides a set of services. Different platforms, or different versions of the ROM monitor for a single
platform, may implement fewer or extra service. The table has room for growth, and any entries which are not
supported map to a NOP-service (when called it returns 0 (false)).
A client of a service should either be selected by configuration, or have suitable fall back alternatives in case the
feature is not implemented by the ROM monitor.
Note:: Checking for unimplemented service when this may be a data field/pointer instead of a function: suggest
reserving the last entry in the table as the NOP-service pointer. Then clients can compare a service entry with
this pointer to determine whether it’s initialized or not.
The header file cyg/hal/hal_if.h defines the table layout and accessor macros (allowing primitive type checking
and alternative implementations should it become necessary).
The source file hal_if.c defines the table initialization function. All HALs should call this during platform ini-
tialization - the table will get initialized according to configuration. Also defined here are wrapper functions which
map between the calling interface API and the API of the used eCos functions.
Implemented Services
This is a brief description of the services, some of which are described in further detail below.
VERSION
Version of table. Serves as a way to check for how many features are available in the table. This is the index
of the last service in the table.
KILL_VECTOR
[Presently unused by the stub code, but initialized] This vector defines a function to execute when the system
receives a kill signal from the debugger. It is initialized with the reset function (see below), but the application
(or eCos) can override it if necessary.
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