Oric Telestrat-specific information for cc65


An overview over the Telestrat (Telemon 2.4 & Telemon 3.x : http://orix.oric.org) runtime system as it is implemented for the cc65 C compiler.

1. Overview

2. Binary format

3. Memory layout

4. Platform-specific header files

5. Loadable drivers

6. Limitations

7. Other hints

8. License

1. Overview

This file contains an overview of the Telestrat runtime system as it comes with the cc65 C compiler. It describes the memory layout, Telestrat-specific header files, available drivers, and any pitfalls specific to that platform.

Please note that Telestrat-specific functions are just mentioned here, they are described in detail in the separate function reference. Even functions marked as "platform dependent" may be available on more than one platform. Please see the function reference for more information.

Oric Telestrat is the last Oric computer (Released in 1986, mainly in France). This computer is an Atmos with extra hardware: RS232, cardridge(banking system), joysticks (2 ports) or mouse (on joystick port), FDC.

Video chip, CPU, keyboard management, tape hardware are the same than Atmos.

Telestrat can start in Atmos mode with Atmos Cardridge (which is only the atmos Basic 1.1 ROM).

Telestrat can start in Sedoric (Atmos OS) and Atmos mode with Stratoric Cardridge. This Cardridge has 3 banks of 16KB of rom with:

The main Telestrat's configuration is the Telemon/Hyperbasic Cardridge inserted with Stratsed in floppy drive.

Anyway, there is no way to load a tape file in Telemon/Hyperbasic mode without alternative program.

There is also no software to write a Stratsed dsk file on PC.

This Telestrat target build an Orix binary file. But, in the future, it will be possible to build a Stratsed disk. Orix uses the same systems calls than Telemon mode.

That is why if you need to do software for telestrat target, you have the choice to:

Telestrat (from cardridge) can handle 8 banks (from $C000 to $FFFF): Bank 0 is the overlay ram. Others banks can be ROM or RAM.

2. Binary format

The standard binary output format generated the linker for the Telestrat target is a machine language program with a 20 bytes header described here

This header is used for Telemon 3.0.

Anyway, for Telemon 2.4, there is no file management, there is no TAPE routine in Telemon, there is no way to load a binary easily.

Stratsed (the Telestrat operating system) handles files management. Stratsed is loaded to memory from floppy disk. Stratsed vector are declared in asminc/telestrat.inc. But, reverse engineering is required to find how these vectors works. Please, note that Stratsed is located in overlay memory (bank 0)

There is no tool to insert a binary in a Stratsed floppy disk.

The only way to load a binary (for Telemon 2.4) is to:

Please note also, that the binary converted into TAP file, will not produce a right stratsed file when tap2dsk and old2mfm are used. You will be in the case that Telestrat/Stratsed crashed when you do "DIR" command.

If you know the Stratsed disk format, please contact the author of this doc.

3. Memory layout

In the standard setup, cc65-generated programs use the memory from $0801 to $9800; so, nearly 37K of memory (including the stack) is available. ROM calls are possible with BRK feature.

Special locations:


The C runtime stack is located at $97FF (or $B3FF), and grows downwards.


The C heap is located at the end of the program, and grows towards the C runtime stack.

4. Platform-specific header files

Programs containing Telestrat-specific code may use the telestrat.h header file.

4.1 Telestrat-specific functions

The functions listed below are special for the Telestrat. See the function reference for declaration and usage.

4.2 Hardware access

The following pseudo variables declared in the telestrat.h header file do allow access to hardware located in the address space. Some variables are structures; accessing the struct fields will access the chip registers.


Access to the VIA (Versatile Interface Adapter) chip is available via the VIA variable. The structure behind this variable is explained in _6522.h.


Access to the VIA2 (Versatile Interface Adapter) chip is available via the VIA2 variable. The structure behind this variable is explained in _6522.h.


Access to the 6551 ACIA chip is available via the ACIA variable. The structure behind this variable is explained in _6551.h.

5. Loadable drivers

5.1 TGI

TGI drivers is available on Oric Telestrat with some functions:

5.2 Extended memory drivers

No extended memory drivers are currently available for the Telestrat. This feature could be done because telestrat can manage RAM inserted in his port cardridge.

5.3 Joystick drivers

Telemon 2.4 returns in keyboard buffer the direction of the joysticks. This means that if you get input from keyboard by conio cgetc function, you will get direction from joysticks.

Anyway, if you don't want to use ROM, you can use joysticks standard drivers in your code.

The standard driver manages two joysticks. Only one button is managed for these joysticks.

Telestrat can handle one button for the left port, and three buttons for the right port (but this port was designed for a mouse).

If you find a Telestrat mouse (which is almost impossible :), these driver will work too because there is some extra hardware in the mouse to send direction.

5.4 Mouse drivers

Telestrat manages also mouse (Joystick port) Telestrat mouse is really difficult to find.

5.5 RS232 device drivers

Telestrat has a RS232 port, but it's not usable in cc65. It is possible to use RS232 port with Telemon calls (see XSOUT primitive for example)

6. Limitations

6.1 Disk I/O

Telemon 3.0 handles fopen, fread, fclose primitives. It means that this function will crash the Telestrat because Telemon 2.4 does not have these primitives. By the way, Telemon 3.0 uses an extension "ch376 card" which handles sdcard and FAT 32 usb key. In the next version of Telemon, FT DOS, Sedoric, Stratsed will be handled in these 3 primitives (fopen, fread, fclose).

6.2 conio

Functions textcolor and bgcolor are available only with Telemon 3.0 (Orix). Telemon 2.4 primitives can't handle any change of colors in text mode except with XINK or XPAPER primitives which put on the first and second columns ink and paper attributes. The only way to change color on the same line for text is to handle it in pure assembly without systems calls.

7. Other hints

8. License

This software is provided 'as-is', without any expressed or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.