W83791G General Description
W83791D/G is an evolving version of the W83782D/G --- Winbond's most popular hardware status monitoring IC. Besides the conventional functions of W83782D/G, W83791D/G uniquely provides several innovative features such as speech function, ASF sensor compliant, SMBus 2.0 ARP command compatible, VID table selection trapping, and 5VID output control. Conventionally, W83791D/G can be used to monitor several critical hardware parameters of the system, including power supply voltages, fan speeds, and temperatures, which are very important for a high-end computer system to work stably and efficiently. As for data access, W83791D/G provides slave SMBus 2.0 interface which can reply PEC (Packet Error Code) when as ASF sensor.
An 8-bit analog-to-digital converter (ADC) was built inside W83791D/G. W83791D/G can simultaneously monitor 10 analog voltage inputs (including power VDD/5VSB monitoring), 5 fan tachometer inputs, 3 remote temperatures, and one case open detection signal. The sense of remote temperature can be performed by thermistors, 2N3904 NPN-type transistors, or directly from IntelTM CPU with thermal diode output. W83791D/G provides 3 PWM (pulse width modulation) outputs for two modes of smart fan control- Thermal CruiseTM mode and Speed Cruise mode. Under Thermal CruiseTM mode, temperatures of CPU and the system can be maintained within specific programmable ranges under the hardware control. Speed Cruise, namely, is to keep the fan operate in the specific programmable r.p.m. As for warning mechanism, W83791D/G provides speech voice warning, beep tone warning, and SMI#, OVT#, IRQ signals for system protection events.
Additionally, 5 VID inputs are provided to read the VID of CPU (i.e. PentiumTM II/III) if applicable.
These VID inputs provide the information of Vcore voltage that CPU expects. Furthermore, W83791D/G provides programmable VID output control to alter the voltage CPU consumes.
W83791D/G also uniquely provides an optional feature: early stage (before BIOS was loaded) beep / speech warning to detect if the fatal elements present --- Vcore or +3.3V voltage fail and thus the system can not be boomed up. If the VSB power on setting refers to Intel VRM 9.x, the VID table within W83791D/G will be according to the new one. W83791D/G also has 2 specific pins to provide
selectable address setting for application of multiple devices (up to 4 devices) wired through I2CTM interface.
W83791D/G speech function is enabled by building in a programmable speech synthesizer with a 9-bit current DAC output as well as a connectable external flash memory for storing voice data.
W83791D/G supports 1 CPU present or absent event trap, 5 external event traps, 17 hardware monitor event traps (10 analog voltage, 3 fan tachometer, 3 remote temperature, 1 case open) and 128 internal programmable event traps, amounting to 151 different speech outputs. If more than two events happen simultaneously, the priority set is: SLOTOCC# > EVNTRP1 > EVNTRP2 > EVNTRP3 > EVNTRP4 > EVNTRP5 > 128 Programmable events (Bank0 index 09h) > 17 Hardware status events. Voice data stored in the external flash memory interface with Winbond W55FXX is flexible to change by Winbond application software and on-line programming flash data is provided also. Besides, an external resistor is added to provide ring oscillator.
When you do not use the speech function, W83791D/G provides a set of flexible I/O control functions to the system designer through a set of General Purpose I/O ports. These GPIO ports may serve as simple I/O or may be individually configured to provide a pre-defined alternate function. If pin 9 (SPEECH_SEL) is trapped to high at VSB power on, this function will be active.
W83791D/G can uniquely serve as an ASF sensor to respond to ASF master's request for the implementation of network management in OS-absent state. Through W83791D/G compliance with ASF sensor spec, network server is able to monitor the environmental status of the client in OS-absent state by PET frame values returned from W83791D/G, such as temperatures, voltages, fan speed, and case open. Moreover, W83791D/G supports SMBus 2.0 ARP command to solve the problem of address conflicts by dynamically assigning a new unique address to W83791D/G after W83791D/G's UDID is sent.
Through the application software or BIOS, the users can read all the monitored parameters of the system from time to time. A pop-up warning can also be activated when the monitored item is out of the proper/preset range. The application software could be Winbond's Hardware DoctorTM, IntelTM LDCM (LanDesk Client Management), or other management application software. Besides, the users can set up the upper and lower limits (alarm thresholds) of these monitored parameters and activate one programmable and maskable interrupts. An optional beep tone could be used as a warning signal when the monitored parameters are out of the preset range.