Rastergraf Topaz, User Manual

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Rastergraf
Programming On-board Devices and Memories 5-19
5.5 System Management Devices and Functions
The Topaz/Stratus/Garnet boards have devices that are specifically
intended to assist in system management. These include:
•
A National Semiconductor LM75 I
2
C temperature sensor located
near the SM731 chip provides local temperature measurements.
You can obtain the data sheet and collateral information for the
LM75 from the technical document section on the Rastergraf web
site;
•
A 2 Kb I
2
C Serial EEPROM which can be used by system software
to store data such as serial number and software revision;
•
In addition, there are features of the SM731 chip that are useful:
•
Power management control registers allow various parts of the
chip to be put powered down without making the chip entirely
useless;
•
Signature registers in the RAMDAC can be are used to confirm
that a test pattern in display memory will pass correctly through
the SM731 all the way to the DAC inputs. This is useful as a Built
In Self Test (BIST) function;
•
When the board is properly connected to a monitor and a test
image is displayed on the monitor, a certain level voltage will be
developed at the DAC outputs that drive the monitor. A simple
A/D reads the voltage and confirms that the DAC output is above a
certain threshold level;
•
The I
2
C-based DDC2B protocol is used to control the display
monitor. DDC2B is a VESA standard ( http://www.vesa.org/ )
which allows the frame buffer to read the Additional Display
Identification Data (EDID) from the monitor. The EDID includes
resolutions supported, maximum width and refresh, and sync type;
•
Frequency select bits for the SM731 Drawing Engine and the
programmable Memory Clock PLL allow the system to optimize
operating frequencies for the SM731 as a function of system
temperature.
Please contact Rastergraf for more information if you wish to utilize any
or all of these features.