W83791D Datasheet, PDF (17/46 Pages) Winbond – W83791D Winbond H/W Monitoring IC

W83791D
Preliminary
6. FUNCTION DESCRIPTION
6.1 General Description
The W83791D provides 10 analog positive inputs, 5 fan speed inputs , at most 5 sets for fan PWM (Pulse
Width Modulation) control, 3 thermal inputs from remote thermistors ¡ B2N3904 transistors or Pentium^TM II/III
(Deschutes) thermal diode outputs, case open detection and beep function output when the monitored values exceed
preset ranges , including the voltage, temperature, and fan count. Moreover, W83791D uniquely provides several
innovative and practical functions to make the whole system more efficient and compliant with future trend of
network management, such as speech function, ASF sensor compliant, SMBus 2.0 ARP command compatible, VID
table selection trapping, 5VID output control, and so forth. Once the monitoring function ofW83791D is enabled,
the watch dog machine will monitor every function and store the values to registers for comparison with preset
ranges. If the monitoring value exceeds the limit value, the interrupt status will be set to 1 and W83791D will issue
interrupt signals such as SMI# and IRQ if not masked..
6.2 Access Interface
The W83791D provides I²C Serial Bus for microprocessor to read/write internal registers. In the W83791D,
there are three serial bus addresses. Through the first address defined at CR[48h], all the registers can be read and
written except CPUT1/CPUT2 temperature sensor registers. The read/write of the CPUT1/CPUT2 temperature
sensor registers can be implemented through the second address (defined at CR[4Ah] bit2-0) and the third address
(defined at CR[4Ah] bit6-4).
The first serial bus address of W83791D has 2 hardware setting bits set by pin10-11. The address is
001011[pin11][pin10]. Hence, the content of CR[48h] would be 00101110 if pin11=1 and pin10=0 .
6.2.1 The first serial bus access timing
(a) Serial bus write to internal address register followed by the data byte
0
SCL
780
78
SDA
0
Start By
Master
10110
Frame 1
Serial Bus Address Byte
SCL (Continued)
1 R/W
D7 D6 D5 D4 D3 D2 D1 D0
Ack
Ack
by
by
Frame 2
791D
791D
Internal Index Register Byte
0
78
SDA (Continued)
D7 D6 D5 D4 D3 D2 D1 D0
Frame 3
Data Byte
Ack
by
78941RD
Stop
by
Master
Figure 1. Serial Bus Write to Internal Address Register followed by the Data Byte
10
Publication Release Date: Aug, 2001
Revision 0.41