Rainbow Electronics MAX1669 User Manual

Page 13

GPIO Data Register

I/O1 and I/O2 are configured through the GPIO data
register and CONFIG byte register (Table 7 and Table 3).
Upon power-up, the GPIOs are set as inputs. To ensure
the I/Os are configured as inputs, set the state of the
DATA1 and DATA2 bits high within the GPIO data reg-
ister for I/O1 and I/O2, respectively. Figure 4 shows that
by setting the GPIO DATA_ bits high, the open-drain
FET connected to the I/O_ pins goes high impedance.
Next, clear the MASK1 and MASK2 bits low within the

CONFIG byte register to remove the masks on the
ALERT interrupts for I/O1 and I/O2, respectively.

To use I/O1 or I/O2 as an output, first set the MASK1
and MASK2 bits high, respectively. Setting the MASK_
bits high within the CONFIG byte register masks out the
corresponding I/O ALERT interrupts. Since the internal
FETs are open-drain, a pull-up resistor is required from
I/O_ to V

. The DATA1 and DATA2 bits within the

GPIO data register directly control the state of the out-
puts of I/O1 and I/O2, respectively (Figure 4).

MAX1669

Fan Controller and Remote Temperature Sensor

with SMBus Serial Interface

______________________________________________________________________________________

BIT

NAME

FAN duty-factor control bit

3–0

RFU

Reserved for future use

FAN duty-factor control bit

7 (MSB)

FUNCTION

FAN duty-factor control bit

FAN duty-factor control bit. D3–D0 are decoded as follows:
D3–D0

Duty

OUT

(nominal)

0000b

0001b

6.67%

0.0625

0010b

13.33%

0.125

0011b

20%

0.1875

0100b

26.67%

0.25

0101b

33.33%

0.3125

0110b

40%

0.375

0111b

46.67%

0.4375

1000b

53.33%

0.5

1001b

60%

0.5625

1010b

66.67%

0.625

1011b

73.33%

0.6875

1100b

80%

0.75

1101b

86.67%

0.8125

1110b

93.33%

0.875

1111b

100%

0.9375

Table 6. Fan Duty-Factor Data Byte Bit Assignments (Write Command = 1Bh)

ALERT

MASK_ BITS

GPIO DATA_ BITS

DELAY

I/O_ PIN

ALERT RESPONSE

Figure 4. GPIO Logic Diagram