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MAX7314

18-Port GPIO with LED Intensity Control, Interrupt, and Hot-Insertion Protection

Maxim Integrated 

18-Port GPIO with LED Intensity Control,

Interrupt, and Hot-Insertion Protection

Port Inputs and Transition Detection

Input ports registers reflect the incoming logic levels of

the port pins, regardless of whether the pin is defined

as an input or an output. Reading an input ports regis-

ter latches the current-input logic level of the affected

eight ports. Transition detection allows all ports config-

ured as inputs to be monitored for changes in their

logic status. The action of reading an input ports regis-

ter samples the corresponding 8 port bits’ input condi-

tion. This sample is continuously compared with the

actual input conditions. A detected change in input

condition causes the INT/O16 interrupt output to go

low, if configured as an interrupt output. The interrupt is

cleared either automatically if the changed input

returns to its original state, or when the appropriate

input ports register is read.

The INT/O16 pin can be configured as either an inter-

rupt output or as a 17th output port with the same static

or blink controls as the other 16 ports (Table 4).

Port Output Control and LED Blinking

The two blink phase 0 registers set the output logic lev-

els of the 16 ports P0–P15 (Table 8). These registers

control the port outputs if the blink function is disabled.

A duplicate pair of registers, the blink phase 1 registers,

are also used if the blink function is enabled (Table 9).

In blink mode, the port outputs can be flipped between

using the blink phase 0 registers and the blink phase 1

registers using hardware control (the BLINK input)

and/or software control (the blink flip flag in the configu-

ration register) (Table 4). The logic level of the BLINK

input can be read back through the blink status bit in

the configuration register (Table 4). The BLINK input,

therefore, can be used as a general-purpose logic input

(GPI port) if the blink function is not required.

PWM Intensity Control

The MAX7314 includes an internal oscillator, nominally

32kHz, to generate PWM timing for LED intensity control.

PWM intensity control can be enabled on an output-by-

output basis, allowing the MAX7314 to provide any mix

of PWM LED drives and glitch-free logic outputs (Table

10). PWM can be disabled entirely, in which case all out-

put ports are static and the MAX7314 operating current

is lowest because the internal oscillator is turned off.

PWM intensity control uses a 4-bit master control and 4

bits of individual control per output (Tables 13, 14). The

4-bit master control provides 16 levels of overall intensi-

ty control, which applies to all PWM-enabled output

ports. The master control sets the maximum pulse

width from 1/15 to 15/15 of the PWM time period. The

individual settings comprise a 4-bit number, further

reducing the duty cycle to be from 1/16 to 15/16 of the

time window set by the master control.

For applications requiring the same PWM setting for all

output ports, a single global PWM control can be used

instead of all the individual controls to simplify the con-

trol software and provide 240 steps of intensity control

(Tables 10 and 13).

Standby Mode

When the serial interface is idle and the PWM intensity

control is unused, the MAX7314 automatically enters

standby mode. If the PWM intensity control is used, the

operating current is slightly higher because the internal

PWM oscillator is running. When the serial interface is

active, the operating current also increases because

the MAX7314, like all I2C slaves, has to monitor every

transmission.

SDA

tLOW

tSU,DAT

tHD,DAT

tSU,STA

tHD,STA

tBUF

tSU,STO

SCL

tHIGH

tHD,STA

tR

tF

START CONDITION

REPEATED START CONDITION

STOP

START

CONDITION CONDITION

Figure 2. 2-Wire Serial Interface Timing Details

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