Orban OPTIMOD 6200, Operating Manual

Page: 159 / 195

OPTIMOD TECHNICAL DATA
6-17
AES/EBU transmitter when an output sample rate is required that is synchronous
to the input or sync input sample rate (external sync).
The inter-chip serial data format, the input MCK multiplication factor, and the
user and output channel status data are controlled by the Z-180 via internal con-
trol registers and data memory accessed through the parallel port made up of the
5-bit address bus (pins 9-13), the 8-bit data bus (pins 1-4, 21-24), and the
S C
and
WR RD/
control pins (pins 14 and 16) of IC603. IC603 pin 15 interrupts the Z-180
when its internal registers can be written with user data.
The on-chip RS422 line driver provided by IC603 is a low skew, low impedance,
differential output capable of driving a 110
Ω
transmission line with a 4Vp-p sig-
nal. Shielded 1:1 pulse transformer T601 transmits the differential digital output
signal to XLR connector J601.
DSP Circuits
The DSP circuits consist of eight general-purpose DSP chips that execute DSP software
code to implement digital signal processing algorithms.
The algorithms filter, compress, and limit the audio signal. The eight DSP chips, each
operating at 37 million instructions per second (MIPS) for a total of 295MIPS, provide
the necessary signal processing. A 48kHz sampling rate is used. Two of the on-board
serial audio interface (SAI) peripherals on each DSP chip are used to transfer data chip-
to-chip at a 24.576Mbit/s rate, maintaining a 24-bit word length. The DSP chips are cas-
caded, processing the audio serially. The first chip receives the analog input via the A/D
chip and the digital input via the SRC chip. Input source selection is performed seam-
lessly, internal to the DSP chip.
During system initialization (which normally occurs when power is first applied to the
6200), and when processing algorithms are changed, the Z-180 downloads the DSP ex-
ecutable code stored in the ROM, via the serial host interface (SHI) port of each DSP
chip. Once a DSP chip begins executing its program, execution is continuous. The Z-180
provides the DSP program with parameter data (representing information like the set-
tings of various processing controls), and extracts the front panel metering data from the
DSP chips via this same SHI port.
The “analog” and digital outputs are sent to the D/A and the output SRC chips via the
SAI port of the last DSP chip, IC707.
Component-Level Description:
IC700 through IC707 are the DSP chips.
CAUTION: Do not attempt to remove these chips from the PCB. These chips