linux/Documentation/smsc_ece1099.txt
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   1What is smsc-ece1099?
   2----------------------
   3
   4The ECE1099 is a 40-Pin 3.3V Keyboard Scan Expansion
   5or GPIO Expansion device. The device supports a keyboard
   6scan matrix of 23x8. The device is connected to a Master
   7via the SMSC BC-Link interface or via the SMBus.
   8Keypad scan Input(KSI) and Keypad Scan Output(KSO) signals
   9are multiplexed with GPIOs.
  10
  11Interrupt generation
  12--------------------
  13
  14Interrupts can be generated by an edge detection on a GPIO
  15pin or an edge detection on one of the bus interface pins.
  16Interrupts can also be detected on the keyboard scan interface.
  17The bus interrupt pin (BC_INT# or SMBUS_INT#) is asserted if
  18any bit in one of the Interrupt Status registers is 1 and
  19the corresponding Interrupt Mask bit is also 1.
  20
  21In order for software to determine which device is the source
  22of an interrupt, it should first read the Group Interrupt Status Register
  23to determine which Status register group is a source for the interrupt.
  24Software should read both the Status register and the associated Mask register,
  25then AND the two values together. Bits that are 1 in the result of the AND
  26are active interrupts. Software clears an interrupt by writing a 1 to the
  27corresponding bit in the Status register.
  28
  29Communication Protocol
  30----------------------
  31
  32- SMbus slave Interface
  33        The host processor communicates with the ECE1099 device
  34        through a series of read/write registers via the SMBus
  35        interface. SMBus is a serial communication protocol between
  36        a computer host and its peripheral devices. The SMBus data
  37        rate is 10KHz minimum to 400 KHz maximum
  38
  39- Slave Bus Interface
  40        The ECE1099 device SMBus implementation is a subset of the
  41        SMBus interface to the host. The device is a slave-only SMBus device.
  42        The implementation in the device is a subset of SMBus since it
  43        only supports four protocols.
  44
  45        The Write Byte, Read Byte, Send Byte, and Receive Byte protocols are the
  46        only valid SMBus protocols for the device.
  47
  48- BC-LinkTM Interface
  49        The BC-Link is a proprietary bus that allows communication
  50        between a Master device and a Companion device. The Master
  51        device uses this serial bus to read and write registers
  52        located on the Companion device. The bus comprises three signals,
  53        BC_CLK, BC_DAT and BC_INT#. The Master device always provides the
  54        clock, BC_CLK, and the Companion device is the source for an
  55        independent asynchronous interrupt signal, BC_INT#. The ECE1099
  56        supports BC-Link speeds up to 24MHz.
  57
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