
SMH4814 
Preliminary Information 
Summit Microelectronics, Inc 
2080  2.0  07/21/05 
19 
Command Register: 
The command register (Table 1) provides useful 
software functionality for the SMH4814.  It is accessed 
using the 1001 slave address, and a word address of 
0x000.  To invoke any of the functions of the 
command register, simply write a “1” to the appropriate 
bit position.  The other bits should receive a “0”.  Note 
that invoking contradictory commands, such as Power 
Down and Power Up, simultaneously will cause 
indeterminate results. The following table describes 
the command byte: 
Bit 
Description 
7 
Clear Fault 
6 
Check Fuse 
5 
Clear WP 
4 
Set WP 
3 
Check Short FET 
2 
Forced Shut Down 
1 
Power Down 
0 
Power Up 
Table 1 – Command Register 
Status/Fault Registers: 
There are three Status/Fault Registers, accessed at 
slave address 1001 with address bit A8 set low, at 
word address 0x02-0x04. These registers generally 
act as status registers, giving the user the current 
state of the device.  However, when a fault occurs, the 
state of the device becomes latched, allowing the user 
to access the state of the part at the time of fault.   
Once latched into the Fault state, the only way to set 
these registers back to Status registers is to use the 
command register to clear the fault.  
Refer to the Status/Fault Register Tables (page 40) for 
more detailed information about the meaning of each 
bit. 
Serial Interface
The SMH4814 uses the industry standard I
2
C, 2-wire 
serial data interface. This interface provides access to 
the general purpose EEPROM, the command and 
status registers, and the configuration registers. The 
interface has two address inputs A1 and A2 
(determined by R0F[7:6]), allowing up to four devices 
on the same bus. This allows multiple devices on the 
same board or multiple boards in a system to be 
controlled with two signals; SDA and SCL. 
Device configuration utilizing the Windows based 
SMH4814 graphical user interface (GUI) is highly 
recommended. The software is available from the 
Summit website (
www.summitmicro.com
/
). Using the 
GUI in conjunction with this datasheet, simplifies the 
process of device prototyping and the interaction of 
the various functional blocks. A programming Dongle 
(SMX3200) is available from Summit to communicate 
with the SMH4814. The Dongle connects directly to 
the parallel port of a PC and programs the device 
through a cable using the I
C bus protocol. 
 APPLICATIONS INFORMATION (CONTINUED)