Msc Keyboard Scan Expansion/GPIO Expansion device¶
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.
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.
- 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.