The Primus 68K industry computer 



With the intention to develop a reliable and powerful QL compatible computer 
which could be used countinuously in an industrial environment a modular 
computer system has been developed. It has five main components. 
    micro computer 
    QL compatible add on board 
    backplane with 7 slots 
    expansion cards 
    19 inch case and power supply 
1. micro computer 
The microcomputer is an independent system, which can be mounted into any 19 
inch case (It measures 220x100 mm). It is build fully in CMOS, therefore the 
power consumption is low and -- if used in a standard temperature area -- 
doesn't need a fan. A 68HC000 CPU at 16MHz combined with 2MByte static RAM gives 
you the necessary power. 
While the QL has its expansion cards area in memory from address 0C0000 to 
0FFFFF the Primus has its one directly under 16MByte and it is nearly 1MByte big 
(from F00000 to FFBFFF). The expansion cards in this area are recognized by the 
MINERVA operating system without any alterations. QDOS has to be altered 
slightly to take care of the new area when searching for expansions. 
The operating system, up to three QL ROM expansions and the boot loader are 
placed within a 128kByte EPROM. This EPROM can be replaced by option by an EPROM 
with a maximal size of 1MByte for additional data. 
The boot loader loads the operating system and the QL ROM expansions into the 
16Bit wide RAM. There the CPU can access it without any wait states. Also, while 
bootloading, date and time will be transmitted to the QL clock from a real time 
clock. The RTC is powered by a special capacitor (1F) while the system is off 
line. 
The microcomputer itself has a socket for an EEPROM (electronical erasable PROM) 
with a size of 128kByte that can be used e.g. for important user specific data. 
A watchdog timer is used to control the program flow. If the normal flow of 
operation is disturbed by any reason and thus the watchdog timer is not reseted 
periodically any more it causes a RESET. The original program can be restarted 
by your boot program. 
Less important for a QL compatible system are the alterable interrupt priorities 
for external and RTC interrupts, the wait states and the error handling after 
bus errors. 
2. QL compatible add on board 
The add on board (160x100 mm) contains the three QL specific components ZX8301, 
ZX8302, IPC 8049 plus 32kByte screen memory. The competing memory accesses of 
the ZX8301 and the micro computer are controlled by a logic circuit, so any 
disturbances are avoided. 
Three 9-pin SUB-D sockets for the two serial ports and a CGA monitor connector 
are connected via IDC plug boards. In the same way connected is a 25-pin SUB-D 
socket for the matrix keyboard. The matrix keyboard is used, because it allows 
you easily to use custom made keyboards. Such custom made keyboards can 
eventually be integrated into the 19 inch case. Optionally the Primus comes with 
a Di-Ren keyboard interface and an IBM AT compatible MFII keyboard. 
3. backplane with 7 slots 
The buffered backplane has a total of seven expansion slots with QL-compatible 
signal occupation. The slots are powered at the backplane side with +5V, +12V 
and -12V. The backplane can be mounted in any 19 inch case. The bus system has 
all necessary signals: adress lines, data lines, DSL, RWL, DTACKL, E, RESETL, 
EXINTL, CLK (16MHz) and FC0,1,2 which are sufficient for most QL expansion 
cards. 
The DSMCL signal line is not used anymore and therefore not necessary anymore!!! 

4. expansion cards 
You can connect each QL compatible expansion card to the bus, provided it does 
not need more than the signals mentioned above. 
The most important expansions are controller cards for hard disk and floppy disk 
drives. For use with control applications cards with analogue and digital input 
and output are a matter of priority. 
Contrary to the QL the bus has a higher phase, therefore expansion cards have to 
be able to treat the higher velocity. For example the access time for EPROM's 
should be less than 150 ns. 
5. 19 inch case and power supply 
The 19 inch case gives you physical stability (compare this with a three to four 
feet long QL!) and protects your Primus from environmental influences. The 
insertion technique simplifies the exchange of single components, you are not 
forced to disassemble the whole case. An industrial power supply (as every other 
component this also comes in 19 inch insertion technique) which can be powered 
within the range of 93V up to 264V allows you to use it everywhere in the world. 
A mains filter additionally takes care of an undisturbed working condition of 
the system. 
 
Ing.Buero Michael Klein
Martinstrasse 23
D-64285 Darmstadt
Germany