SA-3051/SA-3052 Operation Manual
Microprocessor Circuitry
The microprocessor (
µ
P) controls the timing of various events within the SA-3051/SA-3052, writes infor-
mation into its memory, and retrieves that information when needed. In addition, the
µ
P reads the settings
of various switches and maintains the status of the various LED indicators on the front panel. The
µ
P
program is stored in a 512K EPROM (Erasable Programmable Read Only Memory). A 2K CMOS RAM
(Random Access Memory) provides memory for the six display memories, and for scratch-pad memory
used during instrument operation.
Periodically, the microprocessor instructs the A/D converter to make another conversion and then place
the result on the internal data bus. The
µ
P reads this data, and uses it to drive the display and/or memory.
Once the
µ
P has the data from the A/D converter, it performs some math on it (decibel conversion), sends
it to the display, and stores it in the temporary display memory.
When told to store a reading, the
µ
P transfers the contents of the temporary display memory to another
RAM location for safekeeping. On recall, the
µ
P does the opposite, moving the data from RAM to the
temporary display memory.
LED Display
The SA-3051/SA-3052 display gets its data from the
µ
P bus. The display is row and column multiplexed
to conserve power. Eight-bit latches hold the row and column data for each column in the display. The
intersection of a selected row and selected column results in an illuminated LED at that position of the
selected column. A constant-current power supply ensures consistent brightness across the display.
Pink Noise Generator
The pink noise generator uses a series of digital shift registers, connected as a pseudo-random sequence
generator. The output of this generator looks like (and for all practical purposes is) white noise.
The output of the white noise generator drives the pinking filter. This filter applies a precise 3 dB/octave
rolloff to its input signal. The resultant output is pink noise.
The output of the pink noise generator is a 150 mW audio power amplifier IC. The output amplifier has
sufficient output current capability to drive directly into a speaker-impedance (4 ohm) load.
6-2
