STV-DCA/VGA-E01 STMICROELECTRONICS [STMicroelectronics], STV-DCA/VGA-E01 Datasheet - Page 20

• Manufacturer Part Number: STV-DCA/VGA-E01
• Description: Low Cost Digital Camera (LCDC) Chipset
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Digital Camera Chipset; Customer Datasheet, Rev 3.0, March 2000
refresh from STV0680A takes place.
4.3.4
The SDRAM initialisation period is currently set to 981 S in STV0680A.
4.4
STV0680A includes a USB Version 1.1 compliant Universal Serial Bus Interface, including a transceiver. This allows direct
connection from STV0680A to a USB connector with minimal additional hardware (i.e. a small number of passive discretes) - see
Section 9.
The USB interface interfaces the STV0680A to the USB at full speed 12MHz data rate. Some of the features are:
USB drivers are supplied by ST. For USB timing information, please refer to the USB specification V1.1.
4.5
The UART module on STV0680A provides a 115200 baud full duplex interface to an external Host.
4.5.1
STV0680A does not support direct connection to a serial link. Physical line driver circuitry is required, e.g. using a standard
RS232 transceiver chip, or by using a small number of low cost discretes (as shown in Section 9.). The schematics shown
assume a 3 core cable with a length of no greater than 2m. Unscreened cable can be used, a suitable low cost connector is a
3.5mm audio jack plugs/sockets.
4.5.2
Receiving data
The UART module in STV0680A receives serial data through the RXD pin. Data reception is initiated by a 1-to-0 transition on
RXD, and the received data is sampled every 8.66 S.
If the RXD input is not 0 when the incoming data is first sampled, the UART module goes back to look for another 1-to-0
transition. This is to provide rejection of false start bits. If the start bit proves valid, reception of the rest of the frame will proceed.
Transmitting data
When a transmission is activated by STV0680A, the contents of an internal transmit shift register are shifted onto the TXD pin,
every 8.66 S.
The UART operates at 12MHz, which is not an integer multiple of 115200, so the actual baud rate is 115232 +/- 0.3%, which is
well within the requirements of a typical 16x oversampling UART, which can tolerate a 3.75% error in baud rate.
4.6
STV0680A and the SDRAM require a 3.3V supply. Where a VV6410 or VV6500 (3.3v) sensor is used, a single voltage regulator
can be used to regulate the supply for all three components from the battery, or the sensor on-board VReg can be used. Where a
VV6444 is used, the sensor requires a 5V supply, hence a DC-DC converter is recommended to provide enough voltage when
the camera is powered from the USB bus. These are explained more fully in the reference design.
STV0680F_contents.fm
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Compliant with USB protocol revision 1.1.
USB protocol handling.
USB device state handling.
Clock and data recovery from USB.
Bit stripping and bit stuffing functions.
CRC5 checking, CRC16 generation and checking.
Serial to parallel conversion.
Single bulk end point.
USB interface
UART module for RS232 interface
Power management and battery type
SDRAM initialisation Period
RS232 Physical interface
UART Module Overview
Commercial in confidence
CDSTV0680F-C
PRELIMINARY
STV0680A + VV6444/6410/6500
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