ASX340CS datasheet(27/74 Pages) ONSEMI

27 / 74 page

ASX340CS_DS Rev. F Pub. 6/15 EN

©Semiconductor Components Industries, LLC, 2015.

ASX340CS: 1/4-Inch Color CMOS NTSC/PAL Digital Image Sensor

External Signal Processing

Device Configuration

After power is applied and the device is out of reset by de-asserting the RESET_BAR pin,

it will enter a boot sequence to configure its operating mode. There are essentially three

three configuration modes: Flash/EEPROM Config, Auto Config, and Host Config. Figure

14: “Power-Up Sequence – Configuration Options Flow Chart,” on page 22 contains

more details on the configuration options.

The SOC firmware supports a System Configuration phase at start-up. This consists of

five modes of execution:

1. Flash Detection

2. Flash-Config

3. Auto-Config

4. Host-Config

5. Change-Config (commences streaming - completes the System Configuration mode).

The System Configuration phase is entered immediately after the firmware initializes

following SOC power-up or reset. By default, the firmware first enters the Flash Detec-

tion mode.

The Flash Detection mode attempts to detect the presence of an SPI Flash or EEPROM

device:

• If no device is detected, the firmware then samples the SPI_SDI pin state to determine

the next mode:

– If SPI_SDI == 0 then it enters the Host-Config mode.

– If SPI_SDI == 1 then it enters the Auto-Config mode.

• If a device is detected, the firmware switches to the Flash-Config mode.

In the Flash-Config phase, the firmware interrogates the device to determine if it

contains valid configuration records:

• If no records are detected, then the firmware enters the Auto-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 one of the other mode (auto-config/change-config).

The Auto-Config mode uses the FRAME_VALID, LINE_VALUE, DOUTT_LSB0 and DOUT-

T_LSB1 pins to configure the operation of the device, such as video format and pedestal

(refer to the Developer Guide for more details). After Auto-Config completes the firm-

ware switches to the Change-Config mode.

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 SOC will take no actions until the host issues

commands.

In the Change-Config mode, the firmware performs a 'Change-Config' operation. This

applies the current configuration settings to the SOC, and commences streaming. This

completes the System Configuration phase.

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