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PET32K(P) Manual Page

NAME

pet32k - describes the GeckOS port to the Commodore PET with 32k (40 column graphics keyboard)

DESCRIPTION

The PET is a machine that has a single environment with only 32k usable RAM, and no memory management unit.

Warning
 the following needs to be updated!

BUILDING

To build the program, you have to have my 6502 cross assembler 'xa-2.1.4e' Current testing takes place on 'VICE', the versatile Commodore emulator.

In the file rom.a65, a few options can be set by setting the defines appropriately. See the build section.

Go to the arch/c64/boot directory and type "make" this will build all necessary files in this directory, including links to all important applications. Typing "make osa.d64" will produce a d64 disk image with all necessary files. This disk image can be transfered to a C64 and used.

If you change something in the code and reassemble, check from the file65 output that the data and bss segments don’t overlap. Also the memory that is dynamically allocated starts at $1600 (see arch/c64/c64rom.a65). Only if nothing overlaps there is no danger.

See also build(7).

BUILD OPTIONS

BOOTING

In VICE (i.e. xpet) or on the PET load the (BASIC) program 'loader', which is in the boot directory and the osa.d64 disk image. When run, this program loads the charom, the program ROM and a small machine language program (boot.obj, which is made from boot.a65). It then starts the boot routine that copies the ROMs to their places and jumps to the kernel RESET routine.

USAGE

The video device is able to handle up to two screen output consoles. The Left-Shift+Rvs/Off key switches between the different virtual consoles.

On the first window, a lib6502 "lsh" is started. The lsh is a lib6502 program and is loaded by the init process. The ROM only contains a command to the init process to start the lib6502 program. It uses a relocatable fileformat and can thus started more than once.

In the shell you can use "c:ls" on drives a: (registered devides) If the iec bus works, then drive b: is disk unit 8 and drive c: is disk unit 9.

For the shell commands see the docs. The memory map is described below. When writing and using lib6502 programs they are relocated automagically.

ROM CONFIGURATION

The "ROM" is a boot image that is loaded into memory from start of available memory. The PET ROMs can of course not be replaced, so they still use the memory from $9000 and up. Even the interrupt routine is started in the PET ROM, but the interrupt vectors are modified to point to GeckOS.

In $e8xx of course the I/O area is used.

The configuration can be seen in arch/pet32k/rom.a65.

INCLUDED PROGRAMS

The ROM contains these blocks

devices/devices.a65

This contains the device handlers supported by the architecture (see below)

sysapps/init/init.a65

The init program that starts all other progams, and is also able to restart them when they finish. See startup(7)

sysapps/fs/fsdev.a65

A filesystem driver that allows accessing devices as files (see fsdev(8)). In this configuration, to save memory, ROM access is not built in.

sysapps/fs/fsiec.a65

The filesystem driver for the IEC or IEEE488 interface of the C64. Note that usually the serial IEC is used. Using the PARALLEL define, instead the Commodore IEEE488 interface module is supported.

lsh

This program is loaded from disk into memory and started.

MEMORY MAP

	$0002		ENVSAVE pointer (per environment)
	$0004		TASKSAVE pointer (per tasks)
	$0006		THREADSAVE pointer (per thread)

	$0008		start of zeropage for ROM-based code
	$0090		PET ROM interrupt vectors at $90
	$0094		start of zalloc'able zeropage
	$00ff		end of zeropage

	$0100		start of userspace stack
	$013f		end of userspace stack
	$0140		start of system stack
	$01ff		end of system stack

	$0200		PCBUF communication buffer

	$0300 		data/bss for ROM-based code
	$134c		start of boot ROM
			devices
			init
			fsiec
			lsh
	$5500		Start of malloc'able free memory

	$7800		screen buffer 1
	$7c00		screen buffer 2
	$8000		screen buffer
	$8400 		PET ROM area
	$e800		PET I/O
	$f000 		PET ROM area
	$ffff		end of ROM

SYSTEM SEMAPHORES

These are the system semaphores defined in the C64 port Any program to access the named resource should aqcuire the relevant semaphore before doing so

SEM_PARIEC

Parallel IEEE488 interface (when available)

KERNEL CONFIGURATION

The kernel is configured with these major configuration options:

STACKCOPY

The stack is divided into two parts - one for the system and one for userspace programs. During context switch the userspace stack is copied over into a save area and the stack area from another task is copied in. This allows for an arbitrary number of tasks (in theory).

SYSTEM INTERRUPT

The PET kernel uses a timer interrupt as a 50Hz interrupt source.

SUPPORTED DEVICES

This section describes the devices supported by GeckOS.

VIDEO

The video device provides three virtual consoles.

VIDEO OUTPUT

Video output is taken from the video buffers at $exxx (see memory map above), with a 40 column, 25 rows display, using the C64’s built-in VIC-II chip.

KEYBOARD MAPPING

The keyboard is mapped such that it can run on the real hardware, but also in the real machine.

Here is a comparison of the real machine, VICE (3.4+) and what GeckOS uses.

GeckOS PET (Graphics kbd) VICE (-model 4032) PET (business kbd) VICE (-model 8032)

Ctrl

Left Shift

Left Shift

Repeat

Right Ctrl

Tab

Rvs/Off

Tab

Tab

Tab

Console switch

(single) Shift + Rvs/Off

(single) Right Shift + Tab

Shift + Tab

Shift + Tab

Console mode

(both) Shift + Rvs/Off

(both) Shift + Tab

Repeat + Tab

Right Ctrl + Tab

Logoff

n/a

n/a

Shift + Repeat + Tab

Shift + Right Ctrl + Tab

|

(both) Shift + y

(both) Shift + y

Repeat + y

Right Ctrl + y
Note
 due to the missing extra control keys (or alternatives for them), the PET graphics keyboard uses both shift key as Ctrl and you cannot use Ctrl and Shift in combination.

SEE ALSO

AUTHOR

Written by André Fachat.

REPORTING BUGS