User manual
Page 16
Document No. 80-15151 Issue 6 HEBER LTD
The Pluto 5 128/16 Controller Board is intended for users who require less drive capability or who
wish to run the lamps at 36V. It has ¼ of MPX1 configured as a 16*8 (128) Lamp Drive Array and the
other ¼ configured as a 16*8 (16 seven-segment digits) LED Drive Array.
The other 32*16 Multiplex Array (MPX2) is utilised by adding external low-cost Pluto 5 Multiplex
Expansion Boards, wired to Connector P11. Each board only requires 5 signal wires from P11 plus
Power Supplies.
Pluto 5 Multiplex Expansion Boards will be available in a number of different sizes, but all based on
providing additional 8*8 blocks of either Lamp or LED drivers. Thus, the basic Pluto 5 configuration
may be expanded externally by another 8 blocks which may be any mix of Lamps or LEDs.
Pluto 5 Multiplex Expansion Boards may also be added to Multiplex Array MPX1 (which is already
used by the on-board drivers). Thus, for example, the Pluto 5 128/16 Controller Board, running at
48V, could have Expansion Boards added to increase its drive capability to that of the Pluto 5 256/32
Controller Board.
The Lamp Multiplex Drive Circuitry is designed to drive 12V, 100mA bulbs. However, it is permissible
for a small number (up to 16) of positions to drive either a higher power bulb (12V, 180ma) or a pair of
100mA bulbs. These "high load" positions should be arranged such that no more than one is on any
one Row or Column drive.
Multiplex Array MPX1 has hardware assistance from the FPGA to enable dimming control. Dimming
level may be set independently for each of the 16 Column strobes, e.g. the 8 lamps on one Column
Strobe could be set to one brightness level while the 8 lamps on a different Column Strobe could be
set to another brightness. The overall basic timing of the multiplexing remains under software control
allowing “overdrive” of lamps for special effects.
Multiplex Array MPX2 may be optionally configured with its full 32*16 capacity without the availability
of hardware assisted dimming, or with 16*16 capability with the hardware assisted dimming facility
intact. This option is selected by a bit in the FPGA – see the relevant FPGA User Manual for details.
Dimming is achieved changing the data presented to the Lamp Row/LED Segment drives at an
adjustable time within the 1mS strobe time. Thus each lamp/LED has two bits of data associated with
it in software – the first bit is the data applied during the first part of the 1mS Strobe period, the second
bit is applied during the second period. The duration of the period that the first bit is applied for may be
set in units of 1/16 mS.
The multiplex is software driven. Every 1mS, data for the next strobe is written to the FPGA which in
turn formats and serialises the data before clocking out the MPX1 data to the on-board 4094 shift
registers (U18,U19,U20,U21,U35,U36) and the MPX2 data, via P11, to any Multiplex Expansion
Boards used.
The exact format of the data to be written each millisecond is determined by the design of the FPGA
being used, but in general it is as follows.
• 32 bits of MPX1 Row/Segment data. First period data.
• 32 bits of MPX1 Row/Segment data. Second period data.
• 32 bits of MPX2 Row/Segment data. First period data.
• 32 bits of MPX2 Row/Segment data. Second period data.
• 4 bits defining Column/Digit strobe number to activate.
• 4 bits defining First Period duration (units of 62.5S).
Consult the User Manual of the actual FPGA in use for exact details of operation.