AN746
Rev. 0.1
5
4. Controlling the Si4012
The Si4012 has four pins to interface with the host MCU:
SDN is the shutdown input of the IC. When it is pulled high or left open, the Si4012 goes to its shutdown
state; when pulled low, the Si4012 wakes up.
NIRQ is the interrupt request output that goes low when an enabled interrupt is triggered in the Si4012.
SCL is the SMBus clock.
SDA is the SMBus data.
4.1. Control
The SMBus interface is implemented as a bidirectional 2-wire interface (SCL, SDA) with the host configured as
master and the Si4012 as slave. Both standard (100 kbs) and fast (400 kbs) modes are supported with 7-bit
addressing. The device address is 1110000x, where x is the R/W bit. Since shutdown can be activated, wakeup
can be initiated and interrupts can be polled using the SMBus interface. The minimal necessary control interface
for the Si4012 is only two pins, SDA and SCL.
Figure 3. Minimal MCU Interface
All host commands consist of a 1-byte opcode followed by 0 or more arguments. All responses from the 4012
consist of a 1-byte top level status followed by 0 or more data values. Refer to the data sheet for details on the
command structure and command details of the Si4012.
Summary of Contents for Si4012
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