Rainbow-electronics MAX6661 Bedienungsanleitung PDF herunterladen (Seite 9)

a WRITE operation. Figure 4 shows the write cycle.

For single byte commands such as OSHT and SPOR,

the operation need only be 7 bits long where the

READ/WRITE bit is omitted. Here the command is

loaded into the shift register on the rising edge of SC

and the command is decoded during the high period of

the 7th clock pulse. The 7th falling edge of SC shifts the

command from the shift register to the appropriate reg-

ister. CS can then go high after the SC low to CS high

hold time t

CSH

(see SPI AC Timing, Electrical Char-

acteristics). Figure 5 shows the timing waveforms for

the MAX6661’s SPI interface.

Remote Temperature Data Register

Two registers, at addresses 81h and 83h, store the

measured temperature data from the remote diode. The

data format for the remote-diode temperature is 10 bits

+ sign, with each LSB corresponding to 0.125°C, in

two’s complement format (Table 3). Register 83h con-

tains the sign bit and the first 7 bits. Bits 7, 6, and 5 of

read immediately, one after the other, their contents

may be the result of two different temperature measure-

ments, leading to erroneous temperature data. For this

reason, a parity bit has been added to the 81h register.

Bit 4 of this is zero if the data in 81h and 83h are from

the same temperature conversion and 83h is read first.

Otherwise, bit 4 is one. The remaining bits are don’t

cares. When reading temperature data, register 83h

must be read first.

Alarm Threshold Registers

The MAX6661 provides four alarm threshold registers

that can be programmed with a two’s complement tem-

perature value with each LSB corresponding to 1°C.

The registers are T

HIGH

, T

LOW

, T

MAX

, and T

HYST

. If the

measured temperature equals or exceeds T

HIGH

, or is

less than T

LOW

, an ALERT interrupt is asserted. If the

measured temperature equals or exceeds T

MAX

, the

OVERT output is asserted (see the Overtemperature

Output

OVERT

section). The POR state for T

HIGH

MAX6661

Remote Temperature-Controlled Fan-Speed

Regulator with SPI-Compatible Interface

_______________________________________________________________________________________ 9

REGISTERS COMMAND POR STATE FUNCTION

RRL 81h 00000000 Read Remote Temperature Low Byte (3MSBs)

RRH 83h 00000000 Read Remote Temperature High Byte (Sign Bit and First 7 Bits)

RSL 85h 00000000 Read Status Byte

RCL/WCL 87h/92h 00000000 Read/Write Configuration Byte

RFCR/WFCR 89h/94h 00000010 Read/Write Fan-Conversion Rate Byte

RTMAX/WTMAX A1h/A4h 01100100 (+100°C) Read/Write Remote T

MAX

RTHYST/WTHYST A3h/A6h 01011111 (+95°C) Read/Write Remote T

HYST

RTHIGH/WTHIGH 8Fh/9Ah 01111111 (+127°C) Read/Write Remote T

HIGH

RTLOW/WTLOW 91h/9Ch 11001001 (-55°C) Read/Write Remote T

LOW

SPOR F8h N/A Write Software POR

OSHT 9Eh N/A Write One-Shot Temperature Conversion

RTFAN/WTFAN A9h/B2h 00111100 (+60°C) Read/Write Fan-Control Threshold Temperature T

FAN

RFSC/WFSC ABh/B4h 00000000 Read/Write Fan-Speed Control

RFG/WFG ADh/B6h 10000000 Read/Write Fan Gain

RFTP AFh 00000000 Read Fan Tachometer Period

RFTCL/WFTPLP B1h/B8h 11111111 Read/Write Fan Tachometer Period Limit (Fan-Failure Limit)

RFTD/WFTD BBh/BCh 00000001 Read/Write Fan Tachometer Divisor

RFS/WFS BFh/C0h 11111111 Read/Write Full-Scale Register

RM/WM F5h/F6h 00000000 Read/Write Mode Register

ID CODE FDh 01001101 Read Manufacturer ID Code

ID CODE FFh 00001001 Read Device ID Code

Table 2. MAX6661 Command-Byte Bit Assignments

1 2 3 4 5 6 7 8 9 10 11 12 13 14 ... 18 19

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