Re: Ada and Automotive Industry

[John Howard <jhoward@sky.net>]

One niche for microcontrollers in automotives is the implementation of a 
Controller Area Network.  ISO 11898 specifies high-speed CAN, and ISO
11519 specifies low-speed CAN.  Allen-Bradley is promoting a CAN 
implementation called DeviceNet.

As a personal interest I am studying Philips XA (a 16-bit eXtended 
Architecture of 80C51 tailored to real-time, multi-tasking, and hardware 
support for high-level language compilers).  Philips plans to release an
XA derivative having DeviceNet that is intended for the automotive 
industry.

The XA family is well-suited for using Ada 95.  As evidence here's a 
description from the Philips 1995 XA Data Handbook (IC25):

The XA supports:
1. Upward compatibility with the 80C51 architecture.
2. 16-bit fully static CPU with a 24-bit program and data address range.
3. Eight 16-bit CPU registers each capable of performing all arithmetic
   and logic operations as well as acting as memory pointers.  Operations 
   may also be performed directly to memory.
4. Both 8-bit and 16-bit CPU registers, each capable of performing all
   arithmetic and logic operations.
5. An enhanced instruction set that includes bit intensive logic
   operations and fast signed or unsigned 16X16 multiply and 32/16 divide.
6. Instruction set tailored for high-level language support.
7. Multi-tasking and real-time executives that include up to 32 vectored 
   interrupts, 16 software traps, segmented data memory, and banked
   registers to support context switching.
8. Low power operation, which is intrinsic to the XA architecture,
   includes power-down and idle modes.

The XA family provides an upward compatibility path for 80C51 users who
need higher performance and 64k or more of program memory.  The
performance of the XA supports the comprehensive bit-oriented operations
of the 80C51 while incorporating support for multi-tasking operating
systems and high-level languages.  The architecture provides direct
support for the concept of a multi-tasking OS by providing two
(System/User) priviledge levels for isolation between tasks.  High
performance, interrupt driven, multi-tasking applications requiring
protection are feasible with the XA.  The present speed of the XA is 10 to 
100 times that of the 80C51.

The Special Function Register (SFR) bus provides a common interface for 
the addition of any new functions to the XA core, thus supplying the means
for building a large and varied microcontroller derivative family.  The XA 
is inexpensive enough to compete in the market for high-volume, low-cost 
applications.

[But is Ada 95 well-suited to support the XA family of derivatives?
Very much so.

One example: the bit level capability of Ada matches perfectly with the
hardware of the XA.  Likewise the Ada support of tasking, exceptions, and
interrupt handling matches with the hardware of the XA.  Plus the 
hierarchical organization of the Ada library can easily accomodate the
logical expansion of the XA family of derivatives.

Ada 95 supports distributed systems.  The system on which a distributed
program runs consists of one or more processor nodes and zero or more
storage nodes.  There will be market opportunities where using multiple XA
devices are more cost effective and powerful than using a 32-bit or larger
microcontroller solution.  A distributed system using DeviceNet as the 
communication subsystem is most probable.

Fundamentally the high level of detail that can be specified with Ada 95
allows for the possibility of highly effective compiling.  In the case of
the XA, the instruction set has been made powerful and efficient with the
addition of several different types of addressing modes.  The formats have
been chosen to optimize the length and execution speed of those 
instructions that would be used the most often in critical code.

The safety checks of Ada tend to simplify debugging.  The XA further
simplifies debugging by providing a Trace Mode, and a software breakpoint 
instruction.  Trace Mode supports user-supplied debugger/monitor programs
which can single-step through any code, even code in ROM.  Only code
executing in System Mode can activate or turn off Trace Mode.

In conclusion, many features of Ada 95 closely complement the hardware
facilities of the XA to aid the goal of reliably controlling complexity.]

-- John Howard <jhoward@sky.net>               -- Team Ada  Team OS/2 --