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+What is smsc-ece1099?
+----------------------
+
+The ECE1099 is a 40-Pin 3.3V Keyboard Scan Expansion
+or GPIO Expansion device. The device supports a keyboard
+scan matrix of 23x8. The device is connected to a Master
+via the SMSC BC-Link interface or via the SMBus.
+Keypad scan Input(KSI) and Keypad Scan Output(KSO) signals
+are multiplexed with GPIOs.
+
+Interrupt generation
+--------------------
+
+Interrupts can be generated by an edge detection on a GPIO
+pin or an edge detection on one of the bus interface pins.
+Interrupts can also be detected on the keyboard scan interface.
+The bus interrupt pin (BC_INT# or SMBUS_INT#) is asserted if
+any bit in one of the Interrupt Status registers is 1 and
+the corresponding Interrupt Mask bit is also 1.
+
+In order for software to determine which device is the source
+of an interrupt, it should first read the Group Interrupt Status Register
+to determine which Status register group is a source for the interrupt.
+Software should read both the Status register and the associated Mask register,
+then AND the two values together. Bits that are 1 in the result of the AND
+are active interrupts. Software clears an interrupt by writing a 1 to the
+corresponding bit in the Status register.
+
+Communication Protocol
+----------------------
+
+- SMbus slave Interface
+        The host processor communicates with the ECE1099 device
+        through a series of read/write registers via the SMBus
+        interface. SMBus is a serial communication protocol between
+        a computer host and its peripheral devices. The SMBus data
+        rate is 10KHz minimum to 400 KHz maximum
+
+- Slave Bus Interface
+        The ECE1099 device SMBus implementation is a subset of the
+        SMBus interface to the host. The device is a slave-only SMBus device.
+        The implementation in the device is a subset of SMBus since it
+        only supports four protocols.
+
+        The Write Byte, Read Byte, Send Byte, and Receive Byte protocols are the
+        only valid SMBus protocols for the device.
+
+- BC-LinkTM Interface
+        The BC-Link is a proprietary bus that allows communication
+        between a Master device and a Companion device. The Master
+        device uses this serial bus to read and write registers
+        located on the Companion device. The bus comprises three signals,
+        BC_CLK, BC_DAT and BC_INT#. The Master device always provides the
+        clock, BC_CLK, and the Companion device is the source for an
+        independent asynchronous interrupt signal, BC_INT#. The ECE1099
+        supports BC-Link speeds up to 24MHz.