AS0142AT datasheet(13/45 Pages) ONSEMI

13 / 45 page

AS0142AT

www.onsemi.com

Figure 7. Hard Standby Operation

Table 9. HARD STANDBY SIGNAL TIMING

Symbol

Parameter

Min

Typ

Max

Unit

Standby entry complete

–

2 Frames

Lines

Active EXTCLK required after going into STANDBY mode

–

EXTCLKs

Active EXTCLK required before STANDBY

de−asserted

–

EXTCLKs

SOFT STANDBY

A soft standby sequence to AS0142AT can be activated by

writing to a register through the two−wire serial interface.

AS0142AT settings could be preserved.

DEVICE CONFIGURATION

After power is applied and the device is out of reset (either

the power on reset, hard or soft reset), it will enter a boot

sequence to configure its operating mode

. There are

essentially three configuration modes: Flash/EEPROM

Config, Auto Config, and Host Config.

The

AS0142AT

firmware

supports

System

Configuration phase at start−up. This consists of two

sub−groups of execution:

Flash detection, then one of the following:

a. Flash Config

b. Auto Config

c. Host Config

The System Configuration phase is entered immediately

following power−up or reset. Firmware will then performs

Flash Detection that attempts to detect the presence of an SPI

Flash or EEPROM device:

• If a device is detected, the firmware switches to the

Flash−Config mode.

• If no device is detected, the firmware then samples the

SPI_SDI pin state to determine the next mode:

♦ If SPI_SDI is low, then it enters the Host−Config

mode.

♦ If SPI_SDI is high

, then it enters the Auto−Config

mode.

In the Flash Config mode, the firmware interrogates the

device to determine if it contains valid configuration

records:

• If no records are detected, then the firmware enters the

Host Config mode.

• If records are detected, the firmware processes them.

By default, when all Flash records are processed the

firmware switches to the Host−Config mode. However,

the records encoded into the Flash can optionally be

used to instruct the firmware to proceed to Auto

Config, or to start streaming (via a Change−Config).

In the Host Config mode, the firmware performs no

configuration, and remains idle waiting for configuration

and commands from the host. The System Configuration

phase is effectively complete and the AS0142AT will take

no actions until the host issues commands

USAGE MODES

How a camera based on the AS0142AT will be configured

depends on what features are used. In the simplest case, an

AS0142AT operating in Auto−Config mode with no

customized settings might be sufficient.

A back−up camera with dynamic input from the steering

system will require a

mC with a system bus interface. Flash

sizes supported up to 2 GB. The two−wire bus is adequate

since only high−level commands are used.

In the simplest case no EEPROM or Flash memory or

is required, as shown in Figure 8.

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