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The CONIO terminal emulator

Although the Durango-X computer is intended to use ad hoc software in standalone cartridges, without the need for any underlying OS, the availability of a console-type I/O is always welcome, allowing easy text display and keyboard interaction.

Firmware Requeriments

As a firmware module, CONIO (CONsole Input/Output) needs some basic support to operate:

  • The CONIO code itself.
  • An 8x8 bitmap font (usually included, but can be switched)
  • A keyboard driver (one for the standard 5x8 matrix keyboard is supplied but, if not detected, paralell input at $DF9A is supported.
  • A minimal interrupt handler which, besides any application-specific needs, should increment the ticks counter and call the keyboard scanning routine.
  • Basic initialisation for all of the above.

You can check an example of the software package installation for CONIO support on the standalone version of EhBASIC from address $E000 on the binary file (label name: reset).

Supported features

CONIO supports both HIRES and colour modes, displaying 32 x 32 or 16 x 16 characters respectively. All four screen areas are supoported and, in case of the first area ($0000-$1FFF) where zeropage & stack reside, it's automatically limited to the bottom half of the screen to protect the important system variables.

Being a bitmap-only display, alternative fonts are supported; just change a pointer to a 2 KiB font definition of your choice (256 chars of 8x8 pixels).


These features have no support from the CONIO interface, and will need to manually set some memory addresses and/or hardware registers.

Character set

CONIO makes use of a slightly custom variant of ISO/IEC 8859-1 for convenience and localisation reasons. C1 control codes, undefined on the standard, are used by:

  • The Sinclair ZX Spectrum semi-graphic characters (128-143, $80-$8F)
  • Selected Greek for Maths based on $E0-$EF of code page 437 (144-159, $90-$9F) but including check mark, approximation and non-strict inequalities.

Other differences:

  • Non-Breaking space (160, $A0) is replaced by a hollow square/rectangle (code 128/$80 Spectrum graphic might be used as a substitute)
  • Currency symbol (164, $A4) is replaced by the Euro sign from ISO 8859-15.
  • Soft hyphen (173, $AD) is replaced by the (seldom found on single-byte encodings!) slashed equal.
  • Cedilla (184, $B8) is replaced by lowercase omega. This encoding is already used on some HD44780-based LCD text displays.
  • Superscript 1 (185, $B9) is replaced by uppercase delta.
  • Fractions (188-190, $BC-$BE) are replaced by the bullet character, the lowercase oe ligature and the eng character.

Codes 191 ($BF) and beyond are the same as ISO 8859-1 -- and also like Windows-1252, for that matter.

extended-ASCII character table

mOS $x0 $x1 $x2 $x3 $x4 $x5 $x6 $x7 $x8 $x9 $xA $xB $xC $xD $xE $xF
$9x α Γ π Σ σ τ ϴ Ω δ
$Ax ¡ ¢ £ ¥ ¦ § ¨ © ª « ¬ ® ¯
$Bx ° ± ² ³ ´ µ · ω Δ º » œ ŋ ¿
$Cx À Á Â Ã Ä Å Æ Ç È É Ê Ë Ì Í Î Ï
$Dx Đ Ñ Ò Ó Ô Õ Ö × Ø Ù Ú Û Ü Ý Þ ß
$Ex à á â ã ä å æ ç è é ê ë ì í î ï
$Fx ð ñ ò ó ô õ ö ÷ ø ù ú û ü ý þ ÿ

C0 Control characters

Usually single-byte sequences for efficiency. Most of bash key shortcuts are implemented here, while a few other are just traditional ASCII. A notable difference is the use of plain CR as newline, unlike the common UNIX (LF) and DOS/Windows (CR plus LF) alternatives.

Some other changes are the cursor up/down (made from VT and LF), the CR-without-LF (used as HOML, line home) and the XON/XOFF, which make little sense on a glass tty but are used instead to enable/disable the cursor.

Colour commands, on the other hand, are generated in a similar way to the ZX Spectrum although with different codes (18 for INK, 20 for PAPER).


When required, the normally hidden glyph is obtained by preceeding the code with a DLE (16/$10).

Ctl-key Dec Hex ASCII name glyph & description effect
- 0 $00 NUL SWTC ▣ square with block (1)
A 1 $01 SOH CRTN ↞ double arrow left carriage return (without line feed)
B 2 $02 STX LEFT ⇦ arrow left cursor left (no backspace)
C 3 $03 ETX TERM ⏻ ball switch send TERM signal(7)/BREAK key (6)
D 4 $04 EOT ENDT ⇲ arrow to SE corner (7)
E 5 $05 ENQ ENDL ↠ double arrow right move cursor to end of line (7)
F 6 $06 ACK RGHT ⇨ arrow right cursor right (no space)
G 7 $07 BEL BELL 🔔 bell acoustic alert
H 8 $08 BS BKSP ⌫ left sign with x backspace, clear previous character
I 9 $09 HT HTAB ⇥ right arrow with bar advance to next tab, printing spaces
J 10 $0A LF DOWN ⇩ arrow down cursor down (no CR)
K 11 $0B VT UPCU ⇧ arrow up cursor up one line
L 12 $0C FF CLRS 𑿄 paper sheet clear screen (2)
M 13 $0D CR NEWL ⏎ angled arrow newline, ZX Spectrum-like
N 14 $0E SO EON ⇒ imply emphasis (inverse) on
O 15 $0F SI EOFF ⇐ reverse imply emphasis (inverse) off
P 16 $10 DLE DLE ♥ heart suit show glyph for next char, do not interpret it (3)
Q 17 $11 DC1 XON ★ star cursor on
R 18 $12 DC2 INK ✏ pencil set foreground colour (3)(4)
S 19 $13 DC3 XOFF ♦ diamond suit cursor off
T 20 $14 DC4 PAPR ♣ club suit set background colour (3)(4)
U 21 $15 NAK HOME ⇱ arrow to NW corner reset cursor without clearing screen
V 22 $16 SYN PGDN ↡ double arrow down page down (7)
W 23 $17 ETB ATYX ♠ spade suit set cursor position (5)
X 24 $18 CAN BKTB ⇤ left arrow with bar backwards tabulation (7)
Y 25 $19 EM PGUP ↟ double arrow up page up (7)
Z 26 $1A SUB STOP ⛔ no entry send STOP signal (7)
- 27 $1B ESC ESC ⬉ NW arrow/mouse cursor escape (7)
- 28 $1C FS PLOT ◢ wedge pointing SE (7)
- 29 $1D GS DRAW ◣ wedge pointing SW (7)
- 30 $1E RS INCG ▒ light pattern (7)
- 31 $1F US TXTM ▓ mid pattern (7)
- 127 $7F DEL DEL ⌧ square with x delete (7)


1.If sent to CONIO, will issue an input.

2.If sent to CONIO, will reset the standard device.

3.Takes a second character to complete.

4.Currently only low nibble used as BgRG or B1 G0 R1 G1 -- official values are 32...47, thus always printable.

5.Takes another TWO chars, ASCII 32 and up, stating row & column (home is 0,0 or ASCII 32,32).

6.Read value from keyboard.

7.Not yet implemented.