Ports Configuration

The 16 I/O ports P0 through P15 can be configured to

any combination of inputs and outputs using the ports

configuration registers (Table 5). The INT/O16 output

can also be configured as an extra general-purpose

output using the configuration register (Table 4).

Input Ports

The input ports registers are read only (Table 6). They

reflect 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 an input

ports register latches the current-input logic level of the

affected eight ports. A write to an 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 an

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

appropriate 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 appropriate 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 MAX7313’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.

INT/O16 Output

The INT/O16 output pin can be configured as either the

INT output that reflects the interrupt flag logic state or

as a general-purpose output O16. When used as a

general-purpose output, the INT/O16 pin has the same

blink and PWM intensity control capabilities as the

other ports.

16-Port I/O Expander with LED Intensity

Control, Interrupt, and Hot-Insertion Protection

______________________________________________________________________________________

13

Table 2. Register Address Map

REGISTER

ADDRESS CODE

(HEX)

AUTOINCREMENT

ADDRESS

Read input ports P7–P0

0x00

0x01

Read input ports P15–P8

0x01

0x00

Blink phase 0 outputs P7–P0

0x02

0x03

Blink phase 0 outputs P15–P8

0x03

0x02

Ports configuration P7–P0

0x06

0x07

Ports configuration P15–P8

0x07

0x06

Blink phase 1 outputs P7–P0

0x0A

0x0B

Blink phase 1 outputs P15–P8

0x0B

0x0A

Master, O16 intensity

0x0E

0x0E (no change)

Configuration

0x0F

0x0F (no change)

Outputs intensity P1, P0

0x10

0x11

Outputs intensity P3, P2

0x11

0x12

Outputs intensity P5, P4

0x12

0x13

Outputs intensity P7, P6

0x13

0x14

Outputs intensity P9, P8

0x14

0x15

Outputs intensity P11, P10

0x15

0x16

Outputs intensity P13, P12

0x16

0x17

Outputs intensity P15, P14

0x17

0x10