Models 707B and 708B Switching Matrix Reference Manual
Section 4: Theory of operations
707B-901-01 Rev. A / August 2010
4-7
Figure 76: Model 707B crosspoint display block diagram
Microcontroller
5x7 dot character displays
Column LED drivers
Rrefresh
Watchdog
12 x 12 High intensity LED array
System
Communication
Serial
Communication
Shut
Off
PWM Signals
Matrix Data
Self-refreshing
Row LED drivers
Slot inidicators
Description of the crosspoint display components
The front panel of the Model 707B is composed of two main display components: a vacuum
fluorescent display (VFD) and a 12 x 12 LED matrix display, called the crosspoint display, that shows
the relay status for each of the slots.
The block diagram shows only the matrix display. Its constituent components are described below.
Microcontroller
The microcontroller receives commands from the main controller and updates the row and column
labels. It also generates the pulse-width modulated (PWM) signals for operating the 12 x 12 LED
matrix.
Row and column labels
The row and column labels are updated by writing to the devices serially. They handle their own
brightness and refresh controls, alleviating the main microcontroller from performing these tasks. As a
result, these are only updated when the data changes and a command from the instrument is issued
to update the label.
