BCM20730 Data Sheet
Mouse Quadrature Signal Decoder
Also, as the n-th row is scanned, the row-hit register is ORed with the current 8-bit row input values if the
current column contains two or more row hits. During the scan of any column, if a key is detected at the current
row, and the row-hit register indicates that a hit was detected in that same row on a previous column, then a
ghost condition may have occurred, and a bit in the status register is set to indicate this.
Scan End
This state determines whether any keys were detected while in the scan state. If yes, the state machine returns
to the scan state. If no, the state machine returns to the idle state, and the 128 kHz clock request signal is made
inactive.
The microcontroller can poll the key status register.
Mouse Quadrature Signal Decoder
The mouse signal decoder is designed to autonomously sample two quadrature signals commonly generated
by optomechanical mouse apparatus. The decoder has the following features:
• Three pairs of inputs for X, Y, and Z (typical scroll wheel) axis signals. Each axis has two options:
– For the X axis, choose P2 or P32 as X0 and P3 or P33 as X1.
– For the Y axis, choose P4 or P34 as Y0 and P5 or P35 as Y1.
– For the Z axis, choose P6 or P36 as Z0 and P7 or P37 as Z1.
• Control of up to four external high current GPIOs to power external optoelectronics:
– Turn-on and turn-off time can be staggered for each HC-GPIO to avoid simultaneous switching of high
currents and having multiple high-current devices on at the same time.
– Sample time can be staggered for each axis.
– Sense of the control signal can be active high or active low.
– Control signal can be tristated for off condition or driven high or low, as appropriate.
Theory of Operation
The mouse decoder block has four 16-bit PWMs for controlling external quadrature devices and sampling the
quadrature inputs at its core.
The GPIO signals may be used to control such items as LEDs, external ICs that may emulate quadrature signals,
photodiodes, and photodetectors.
Shutter Control for 3D Glasses
The BCM20730, combined with the BCM20702, provides full system support for 3D glasses on televisions. The
BCM20702 gets frame synchronization signals from the TV, converts them into proprietary timing control
messages, then passes these messages to the BCM20730. The BCM20730 uses these messages to synchronize
the shutter control for the 3D glasses with the television frames.
BROADCOM
®
September 9, 2013 • 20730-DS108-R
Page 13
BROADCOM CONFIDENTIAL
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