Real World card breadboard. Most cards had a 8255 as basic logic.

The DCE bus on the DAI computer is what makes it more than an standard home computer. The bus offers a structured way to connect peripherials to the computer. Internally the DCE bus is just a 8255 chip. This device offers two 8-bit and two 4-bit I/O ports. Two modes of operation are possible:

• basic mode
• DCE mode

In basic mode only one device can be connected. The ports can be used any way the designer wishes. This mode is ideal for simple (E)PROM programmers.

In DCE mode the port usage is predefined.

• Port A is a bidirectional DATA bus
• Port B is a address bus (4 bits to select a card, 4 bits to address within a card)
• The lower part of the C port is used as control bus:
  • bit 0: bus expand (toggles card 0-15 with 16-31)
  • bit 1: write pulse
  • bit 2: read pulse
  • bit 3: not used

Most cards used a 8255 chip for internal address decoding. So to use the DCE-bus you had to initialise an 8255, and for most cards on the bus, another 8255!

SIGNAL NAME  RWC pin  PC pin
P0B0           24       16   \
P0B1           26       14   |
P0B2           28       12   |
P0B3           30       10   | Databus
P0B4           29        9   | 
P0B5           27       11   |
P0B6           25       13   |
P0B7           23       15   /
P1B0           12       30   \
P1B1           10       31   | Card select
P1B2            8       32   |
P1B3            7       25   /
P1B4            9       24   \
P1B5           11       23   | Internal card addressing
P1B6           13       22   |
P1B7           15       21   /
P2B0           18       26     Bus expand
P2B1           17       27     Write
P2B2           16       28     Read
P2B3           14       29
P2B4           19       20
P2B5           20       19
P2B6           21       18
P2B7           22       17
EXINTR+         4        6     External Interrupt
IN7+            3        5     Parallel input Bit 7(aux. interrupt)
EXRESET         5        7     External Reset (Ground for Reset)
+12V            2        2
+5V            31        1
-5V             1        3
INTR            -       33     INTERRUPT PIN 14 OF CPU 8080
IN7+            -       34
NC              -        8     Not connected
GROUND          6        4

Source: DAI Reference Manual, DAInamic 0/1 (1980) and an Indata DAI folder.

STORAGE OPTIONS

The DAI knew several file storage systems other than audio cassette. Here a list with an indication of access times:

Storage type	storage time 10kByte	command form
Cassette	~160s	SAVE"filename"
MDCR	~43s	CALLM#F000:REM com.
KEN DOS	<3s	CALLM#F000:REM com.
DAI Floppy	~13s	POKE :?"com.": POKE
VC-1541	~27s	real BASIC-commands
DAI-star	?	real BASIC-commands

The DAI-star wasn't just a floppy disk system, but a complete CP/M system, with the extra functionality to act as a DAI file server.

Source: DAInamic 26 & 30 (1985)

DOCUMENTATION

This is the documentation with the DAI:

• DAI personal reference computer manual (both DAI and Indata issue)
• DAInamic magazine 0/1 to 24, 30 and several copies from newer issues
• DAI personal computer schematics sheet 1 to 15
• DAI personal computer firmware manual by B.J.Boerrigter
• and a large pile of copies of almost everything remotely related...

Back to main DAI page

Updated: 2012-05-18

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