Mackie d8b v3, Service Manual

Page: 11 / 117

11
UI SYSTEM
A simplified block diagram of the User Interface system is shown on the next page. Like
the DSP system, an Analog Devices ADSP-2181, is used as the CPU. It controls all functions
and communications within the UI system. Also, like the DSP system, operating
instructions are loaded from the Remote CPU as the system boots. If the UI system does
not ‘find’ the Remote CPU, it will display ‘ERROR 43 HOST COMPUTER NOT FOUND’ in the
VFD.
CLOCKS
Unlike the DSP system, the UI system runs on its own clock. The Clock (Sync) card is for the
DSP system only. Keep the clock’s main spring wound up.
BRAIN BOARD
The Brain Board reads in two types of information from the control surface. Switches are
scanned in through PISO shift registers and transferred to the Brain as serial data. Analog
voltages from faders and V-pots are multiplexed, then sent to an ADC on the Brain
board.
The Brain Board also communicates via UART to all expansion cards. Every card used
in the d8b has a PIC chip. The PIC chip outputs a copyrighted text string so that the d8b
can verify the card is original and Mackie-authorized. Cards in which operating
parameters can be varied are controlled via the Brain (UI System). The Brain Board also
controls all functions on the DCA board.
X1 is the brain processor clock, X2 and X3 are UART clocks.
The Brain board has three status indicators: D3 (green),D2 (yellow), D1 (red).
• If they are all on, it did not read the
EPROM.
• If only the green is on, then it read
the EPROM but did not download
the software.
• When it is running correctly, only the
red LED should be on (and blinking).
CONTROL SURFACE
Control surface LEDs, including V-pot indicators, are updated via SIPO shift registers. To
control the fader motors, serial data is sent from the Brain board to a DAC on the fader
board.
VU METERS
The VU meter LEDs are updated via shift registers but function differently than the control
surface. Remember that the control surface commands are looped through the
Remote CPU; VU meter information is not. The information for the VU meters comes
directly from the DSP Board, and is communicated to the Brain Board via UART.