Documentation/smsc_ece1099.txt

   1 What is smsc-ece1099?
   2 ----------------------
   3
   4 The ECE1099 is a 40-Pin 3.3V Keyboard Scan Expansion
   5 or GPIO Expansion device. The device supports a keyboard
   6 scan matrix of 23x8. The device is connected to a Master
   7 via the SMSC BC-Link interface or via the SMBus.
   8 Keypad scan Input(KSI) and Keypad Scan Output(KSO) signals
   9 are multiplexed with GPIOs.
  10
  11 Interrupt generation
  12 --------------------
  13
  14 Interrupts can be generated by an edge detection on a GPIO
  15 pin or an edge detection on one of the bus interface pins.
  16 Interrupts can also be detected on the keyboard scan interface.
  17 The bus interrupt pin (BC_INT# or SMBUS_INT#) is asserted if
  18 any bit in one of the Interrupt Status registers is 1 and
  19 the corresponding Interrupt Mask bit is also 1.
  20
  21 In order for software to determine which device is the source
  22 of an interrupt, it should first read the Group Interrupt Status Register
  23 to determine which Status register group is a source for the interrupt.
  24 Software should read both the Status register and the associated Mask register,
  25 then AND the two values together. Bits that are 1 in the result of the AND
  26 are active interrupts. Software clears an interrupt by writing a 1 to the
  27 corresponding bit in the Status register.
  28
  29 Communication 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.