STV0674 データシートの表示（PDF） - STMicroelectronics

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STV0674

Tri-mode CMOS digital camera co-processor

STMicroelectronics 

STV0674

STV0674 Functional Description

The VC module varies the compression ratio to match the scene and selected frame rate, to the

FIFO fill state. The VC module is capable of compression ratios of up to 100:1.

Thumbnails can also be generated within the VC for potential display on an image LCD.

The final stage of the VC block manages the data transfer rate from the local VC FIFO store to the

memory or USB core. The VC can perform this management automatically, by employing long-term

(frame-level) and short-term (block-level) compression management.

2.4 Microcontroller

The STV0674 has an embedded high-performance 8052 8-bit microcontroller with 32 Kbytes of

ROM and 32 Kbytes of SRAM available for program memory.

The device functionality provided by default program ROM is generally sufficient to address all

needs of a USB-tethered camera.

In STV0674, code can be executed from the local SRAM as well as default ROM. The default ROM

provides basic functions such as USB control, memory control, VP setup, systems installation, and

the transfer of application specific code into the local SRAM.

In non-tethered applications, the SRAM can be loaded from off-chip EEPROM via I2C or from an

external flash device. If required in tethered applications, the SRAM can be loaded from the host PC

via the USB.

The ROM bootloader will load the application specific firmware code from one of the following

sources, in order of priority:

1 EEPROM.

2 NAND FLASH.

3 PC host (in the case of a webcam).

2.5 Memory interfaces

2.5.1 NAND FLASH memory/SmartMedia card interface

The NAND FLASH module for the STV0674 provides a dedicated interface to an external 32 Mbit to

1 Gbit NAND FLASH chip, and/or 4 Mbyte to 128 Mbyte SmartMedia card.

NAND flash devices can contain a number of bit errors, and the core may deteriorate over time.

Both occurrences are handled automatically by STV0674.

A camera using NAND flash for image storage has the advantage that it can be powered off (e.g.

auto power off, or for changing batteries) without losing images. No serial EEPROM is required as

the application specific programme code can be stored in NAND flash memory.

Note: 1 Support for SMC is for 3V3 cards. 5V cards are not supported.

2 Standard digital camera file formats (e.g. DOS file format, SSFDC) are not supported on SMC cards

at this time.

2.5.2

SDRAM interface

The STV0674 can use SDRAM for image storage and is designed to operate with PC66 or better

compliant devices and supports 16Mbit, 64Mbit and 128Mbit parts in both the x16 SDRAM or x8

DRAM word widths.

It is recommended that any SDRAM used have low self refresh Idd.

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