Thus all major components like the processors, peripheral controllers and
74HC245 buffers are now SMD devices.
SMD DEVICES ON
Dual Port Ram
To avoid confusion, component references in BOLD REFER TO BORIS2 whilst component references in
BOLD ITALICS REFER TO Boris3.
68340 PROCESSOR MEMORY
The SIL extended memory modules (IC106 & IC107),
utilising the MCS3 chip select line, have been replaced by a pair of Flash EPROM
chips (ROM2L & ROM2U).
This means that the battery back up chip DS1210 (IC114)
is no longer required.
A MAX6315 device (U34) is now used to monitor and control the
68340 reset signal. It
issues a master reset to the 68K CPU during power-up, power-down, and brownout conditions.
This master signal is then buffered by two LS04 inverters (U10) before being fed to the rest of the circuit.
Note that U10-E is used to generate
an active high reset signal for the VGA and Floppy Disk Drive devices.
The MAX6315 device offers greater system stability as it is relatively immune to
voltage transients (glitches) on the power supply.
The MAX6315 also has provision for a manual
reset switch (with internal debounce circuitry) - thus isolating the master
reset signal from the external one.
Connecting a 100nF capacitor (C24) from
this external signal to ground also provides additional immunity in noisy
THE ST90 PROCESSOR
The ST90R40 processor (IC300)
on Borris2 will soon become obsolete. We have therefore replaced it with the
As the ST90R50 is equipped with a dedicated address and data bus, the 74LS373 (IC301)
latch used on Borris2 is no longer required.
Two pull-up resistors (R18
& R19) have also been added to the SPI TxD and CLK signals -
again to improve noise immunity.
Two 74HC245 buffers (
U24 and U18) have been added to the ST9 DB Loom (IDC31).
These allow greater integrity of the ST90's address and control signals whilst
driving a capacitive load (i.e. a ribbon cable).
The keyboard connector on Borris3 (DIN1)
has been changed to a Mini-Din one so that it will now accept a standard PC
A pull-up resistor (R16) has also
been added to the clock signal to improve noise immunity.
All DMX outputs on Borris3 are now fitted with protection to 240VAC and also meets EMC immunity
This is achieved by using a pair of 33R 240V PTC thermistors and 5W 6V2 zener
diodes on each of the DMX outputs.
This protection is fitted between the output XLR's and the DMX line drivers
A set of 1W DC-DC converters (NME0505S) are also used to provide an isolated
output to the DMX line drivers (75174) and DMX opto-isolators (6N137). This
provides a 1kVDC isolation.
One DC-DC converter is used to provide isolation for two DMX outputs.
Borris3 also offers Input protection to 240VAC
in the form of two 100R PTC thermistors (PT13 &
PT14) and two transient voltage suppressors (D17 &
DMX input termination is also provided in the form of a 100R PTC thermistor (PT15).
FLOPPY DISK CONTROLLER
The 37C65 Floppy Disk Controller chip (IC505)
used on Borris2 has become obsolete.
This has been replaced by a new 37C78 SMD controller (U505).
The 68340 uses different control signals to control this chip - hence it
requires an updated Katya gal.
Borris3 is now fitted with an optional 20-Way ATX type connector (PSU-ATX).
All fuses are now off the resettable type - once a faulty condition has occurred,
the fuse will trip.
To reset the fuse, simply power down the desk, rectify the fault and
switch the desk back on.
Extra fuses have also been added for the Littlite connector +5V (F5)
and the Qwerty keyboard +5V (F1).
UNIVERSAL SERIAL BUS
A USB port on Borris3 now allows for communication with a standard PC
BORRIS1 TO BORRIS3 UPGRADE
The Borris3 motherboard has been
carefully designed so that it can now be fitted into "old style" Pearl
desks that were fitted with a Borris1 motherboard.
To do this, a Borris3 pcb has to be specially assembled so that none of the
Input/Output connectors are fitted.
Instead, a set of molex headers are fitted in their place which will connect to
connectors on the Pearl rear panel (i.e. DMX XLR's, MIDI & Sound to Light
The VGA Video card is the mounted to Borris3
using four of its fixing holes.