[avr-gcc-list] FREEICE thoughts, maybe offtopic ?

[Armand ten Doesschate]

Hi all,

The reason why I choose to include the parallel port
interface mightnot be clear.
The IEEE1284 defines 4 modes for the parallel port :
1. forward mode (byte wise) in combination with
2. reversed nibble mode and reversed byte mode.
   Those are the "ancient" modes. These modes can control
   the pins individually which are normally used 
   for handshaking
3. EPP mode : this mode can be seen as a sort of address
   and (8 bits) data bus) of the host machine. The pins
   are controled by hardware so cannot be controled individually
   like in 1) and 2). Switching from receiving to transmiting
   and the other way around is very fast. 
4. ECP mode : this can receive and transmit data in one
   direction very fast but switching the direction is takeing
   to much overhead. The pins for handshaking are also controled
   by hardware.

The transfer rate of ECP and EPP mode can be very fast : upto
3Mbytes/s (faster than usb1.1 !) is feasible but depends on both
sides.

The gdb serializer will only support 1), 2) and 3).  4) is used 
default by windoze and can't be switched off easy (as far as
I understood in the past but I am not sure about this).
By all means the gdb serializer should be compatible with
existing parallel port devices.
I must express that the modes to be choosen depend on the host
software. The host software can choose whatever parallel port
is able to support.

I included the parallel port because some cannot use usb (like
old 486 machines) or just don't want to use it.
I managed to demolish a HP usb only printer by connecting it to my
machine and suddenly - after some experimenting of getting 
usb to work - the usb port was gone. I mean that I couldnot see the
printer anymore in GNU/Linux or Windoze (weird ...)

GDB

The gdb serializer host software could talk to the gdb serializer
in 2 ways : either through tcp/ip socket (like avr-gdb) or directly. 
The other ways were not really applicable because one way it should
be a rom emulator so that gdb thinks it is talking to a firmware
rom in an evaluation board, and the other way it should emulate 
a serial port so that gdb thinks it is talking to - again - a
firmware rom in an evaluation board.
The latter two means that the gdb serializer should decode the
gdb remote protocol in order to translate them into appropriate
commands for jtag/bdm. It took me more than 1 week  to fully
understand what this means ... (at least valid upto gdb-5.2)

So I defined a more generally approach in which the gdb serializer
will handle whatever target is connected and whatever protocol
- rs232, jtag, bdm - they will talk. GDB should only use a small
set of commands to talk to the gdb serializer to check the info
or to transmit info to the target. 
This way you can extend the gdb serializer with any protocol without
extending GDB itself with a new protocol. 

Originally I defined the support of the msp430 and - there was some
requests - of the powerpc (MPC567x) series.
But if someone can give me some help what kind of info they use
(reverse engineering, docs ?), then I don't see any reason to handle
those too.

But you have to start somewhere and - last but not least - have time
to spare ...

Question about daisy chaining

Daisy chaining the jtag also depends on the targets : some targets
do support them and some don't. Although I defined the structure
of the gdb serializer for debugging microcontrollers (most of them 
using jtag are a superset of the jtag interface), hardware interfacing
to programmable devices should be possible.


Armand

*******************************************
* choose GNU/Linux : GNU/Linux is Freedom *
*******************************************

----------------------------------

Armand ten Doesschate
Welschapsedijk 141
5652 XL Eindhoven
the Netherlands
tel : (++31) 40 2571 274
e-mail : address@hidden


Armand


*******************************************
* choose GNU/Linux : GNU/Linux is Freedom *
*******************************************

----------------------------------

Armand ten Doesschate
Welschapsedijk 141
5652 XL Eindhoven
the Netherlands
tel : (++31) 40 2571 274
e-mail : address@hidden