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MAX7316

10-Port I/O Expander with LED Intensity Control, Interrupt, and Hot-Insertion Protection

Maxim Integrated 

10-Port I/O Expander with LED Intensity

Control, Interrupt, and Hot-Insertion Protection

Table 2. Register Address Map

REGISTER

Read input ports

Blink phase 0 outputs

Ports configuration

Blink phase 1 outputs

Master, O8 intensity

Configuration

Outputs intensity P1, P0

Outputs intensity P3, P2

Outputs intensity P5, P4

Outputs intensity P7, P6

ADDRESS CODE

(hex)

0x00

0x01

0x03

0x09

0x0E

0x0F

0x10

0x11

0x12

0x13

AUTOINCREMENT

ADDRESS

0x00 (no change)

0x01 (no change)

0x03 (no change)

0x09 (no change)

0x0E (no change)

0x0F (no change)

0x11

0x12

0x13

0x10

Device Reset

The reset input RST is an active-low input. When taken

low, RST clears any transaction to or from the MAX7316

on the serial interface and configures the internal regis-

ters to the same state as a power-up reset (Table 3).

The MAX7316 then waits for a START condition on the

serial interface.

Detailed Description

Initial Power-Up

On power-up, and whenever the RST input is pulled

low, all control registers are reset and the MAX7316

enters standby mode (Table 3). Power-up status makes

all ports into inputs and disables both the PWM oscilla-

tor and blink functionality. RST can be used as a hard-

ware shutdown input, which effectively turns off any

LED (or other) loads and puts the device into its lowest

power condition.

Configuration Register

The configuration register is used to configure the PWM

intensity mode, interrupt, and blink behavior, operate

the INT/O8 output, and read back the interrupt status

(Table 4).

Ports Configuration

The eight I/O ports P0 through P7 can be configured to

any combination of inputs and outputs using the ports

configuration register (Table 5). The INT/O8 output can

also be configured as an extra general-purpose output,

and the BLINK input can be configured as an extra

general-purpose input using the configuration register

(Table 4).

Input Ports

The input ports register is read only (Table 6). It reflects

the incoming logic levels of the ports, regardless of

whether the port is defined as an input or an output by the

ports configuration registers. Reading the input ports reg-

ister latches the current-input logic level of the affected

eight ports. A write to the input ports register is ignored.

Transition Detection

All ports configured as inputs are always monitored for

changes in their logic status. The action of reading the

input ports register or writing to the configuration regis-

ter samples the corresponding 8 port bits’ input condi-

tion (Tables 4, 6). This sample is continuously

compared with the actual input conditions. A detected

change in input condition causes an interrupt condition.

The interrupt is cleared either automatically if the

changed input returns to its original state, or when the

input ports register is read, updating the compared

data (Figure 10). Randomly changing a port from an

output to an input may cause a false interrupt to occur

if the state of the input does not match the content of

the input ports register. The interrupt status is available

as the interrupt flag INT in the configuration register

(Table 4).

The input status of all ports are sampled immediately

after power-up as part of the MAX7316’s internal initial-

ization, so if all the ports are pulled to valid logic levels

at that time an interrupt does not occur at power-up.

______________________________________________________________________________________ 11

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