MIC74_14 Datasheet, PDF (5/20 Pages) Micrel Semiconductor – 2-Wire Serial I/O Expander and Fan Controller

Micrel, Inc.
Timing Definitions
MIC74
Register Descriptions
Table 1. Device Configuration Register
DEV_CFG
D[7]
D[6]
D[5]
D[4]
D[3]
D[2]
D[1]
D[0]
Always write as zero
FAN
IE
Device Configuration Register Parameters
• Power-on default value: 0000 0000_b, 00_h
− Interrupts disabled
− Not in fan mode
• Command_byte address: 0000 0000_b, 00_h
• Type: 8-bits, read/write
• Bit name: IE
• Function: Global interrupt enable
• Operation: 1 = enabled; 0 = disabled
• Bit name: FAN
• Function: Selects fan mode (P[7:4] vs. /FS[2:0],
/SHDN)
• Operation: 1 = fan mode; 0 = I/O mode
• Bit Name: D[2] through D[6]
• Function: Reserved
• Operation: Reserved; always write as zero
Table 2. Data Direction Register
DIR
D[7]
D[6]
D[5]
D[4]
D[3]
D[2]
D[1]
D[0]
DIR7
DIR6
DIR5
DIR4
DIR3
DIR2
DIR1
DIR0
Data Direction Register Parameters
• Power-on default value: 0000 0000_b, 00_h
− All Pn’s configured as inputs
• Command_byte address: 0000 0001_b, 01_h
• Type: 8-bits, read/write
• Bit name: DIRn
• Notes: If the FAN bit of the DEV_CFG register is set to
‘1’ (i.e., if fan mode is selected), P[7:4] are
automatically configured as open-drain outputs. They
are then referred to as /FS[2:0] and /SHDN. The DIR
register has no effect on these I/O bits while in fan
mode.
• Function: Selects data direction, input or output, of Pn
• Operation: 1 = output; 0 = input
•
September 30, 2014
5
Revision 3.0