LM93 datasheet(26/92 Pages) NSC

26 / 92 page

14.0 SMBus Interface (Continued)

Whenever the low byte of a 16-bit register is written, the write

is buffered and does not take effect until the corresponding

high byte is written. If the low byte of a different 16-bit

byte of a 16-bit register, and the corresponding low byte was

not written (or was discarded), then the LM93 will NACK the

byte.

15.0 Using The LM93

15.1 POWER ON

The LM93 generates a power on reset signal on RESET

when power is applied for the first time to the part.

15.2 RESETS

Upon power up, the RESET output is asserted when the

voltage on the power supply crosses the power-on-reset

threshold level (see Electrical Specifications). The RESET

output is open-drain and should be used with an external

pull-up resistor connected to V

DD. Once the power on reset

has completed, the RESET pin becomes an input and when

asserted causes the LOCK bit in the LM93 Configuration

causes the sleep control register to be automatically set to

S4/S5. This causes several error events to be masked ac-

cording to the S4/S5 masking definitions.

Power

On Reset

External

Reset

Factory regs

Power

On Reset

External

Reset

BMC Error Status regs

Host Error Status regs

Value regs

Limit regs

Setup regs

LM93 Configuration Lock Bit

LM93 Configuration GMSK Bit

x (reset)

x (set)

Sleep Mask

Sleep State Control

Other Mask regs

All other registers are not effected by power on reset or

external reset.

15.3 ADDRESS SELECTION

LM93 is designed to be used primarily in dual processor

server systems that may require only one monitoring device.

If multiple LM93 devices are implemented in a system, they

must have unique SMBus slave addresses. See the Section

14.1 SMBUS ADDRESSING for more information.

The board designer may apply a 10 k

Ω pull-down and/or

pull-up resistors to ground and/or to 3.3V SB V

DD on the

ADDR_SEL pin. The LM93 is designed to work with resistors

of 5% tolerance for the case where two resistors are re-

quired. Upon the first SMBus communication to the part, the

LM93 assigns itself an SMBus address according to the

ADDR_SEL input.

Address Select

Board Implementation

SMBus Address

less-than 10% of V

Pulled to ground through a 10 k

Ω resistor

0101,100b

≈ V

DD/2

10 k

Ω (5%) Resistor to 3.3V SB V

DD and to Ground

0101,110b

greater-than 90% of V

Pulled to 3.3V SB V

DD through a 10 k

Ω resistor

0101,101b

15.4 DEVICE SETUP

BIOS executes the following steps to configure the registers

in the LM93. All steps may not be necessary if default values

are acceptable.

Set limits and parameters (not necessarily in this order):

Set up Fan control

Set up PWM temperature bindings

Set fan tach limits

Set fan boost temperature and hysteresis

Set the VRD_HOT and PROCHOT PWM ramp control

rate

Enable Smart Tach Mode and Tachometer Input to PWM

binding (required with direct PWM drive of fans)

Set the temperature absolute limits

Set the temperature hysteresis values

Set temperature filtered or unfiltered usage

Set the Zone Adjustment Offset temperature

Set the PROCHOT override and time interval values

Set the PROCHOT user limit

Enable THERMTRIP masking of error events (if GPIO4

and GPIO5 are used as THERMTRIP inputs)

Set voltage sensor limits and hysteresis

Set the Dynamic Vccp offset limits

Set the Sleep State control and mask registers

Set Other Mask Registers (GPI Error, VRDx_HOT, SC-

SI_TERM, and dynamic Vccp limit checking)

Set start bit to select user values and unmask error events

Set the sleep state to 0

Set Lock bit to lock the limit and parameter registers

(optional)

15.5 ROUND ROBIN VOLTAGE/TEMPERATURE

CONVERSION CYCLE

The LM93 monitoring function is started as soon as the part

is powered up. The LM93 performs a “round robin” sampling

of the inputs, in the order shown below. Each cycle of the

round robin is completed in less than 100 ms.

The results of the sampling and conversions can be found in

the value registers and are available at any time.

LM93 Datasheet(PDF) 26 Page - National Semiconductor (TI)

LM93 Datasheet(HTML) 26 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92

Datasheet Download

Link URL