Dedicated EEPROMs for VESA 2.0 Plug & Play Monitors

Following the success of its ST24LC21 serial EEPROM for "Plug & Play" monitors, SGS-THOMSON has added four new members to this family of Application Specific Memories: the ST24LC21B, ST24LW21, ST24FC21 and ST24FW21. The enlarged family features the world's first devices compatible with the new VESA 2.0 standard which includes an error recovery mechanism.

Plug & Play systems are characterised by the ability to reconfigure themselves automatically whenever a new PC card or peripheral is added to the system. Fundamental to the Plug & Play concept is the use of a non-volatile memory in each peripheral to hold identification information that is used by the PC host to configure its video and graphics subsystems and select appropriate software drivers.

Organised as 128 x 8-bits, the ST24xy21 devices are fully compatible with the VESA Data Display Channel (DDC) standards, communicating both in DDC1 (Transmit Only) and DDC2B (I2C Bidirectional) modes. The devices allow a direct connection between the PC host and the monitor using the standard video cable and 15-pin VGA connector.

The ST24LC21B is fully pin-to-pin compatible with the earlier ST24LC21, as well as with the ST24C21, but, like all of the new devices, offers a Schmitt-Trigger input on the VSYNCH pin for better noise immunity and a higher power-on reset value of 3V. The ST24LW21 is identical to the ST24LC21B except for the write control input on Pin 3 to improve data corruption rejection. The ST24FC21 and ST24FW21 devices offer full VESA 2.0 compatibity, including the error recovery mechanism that allows an automatic return to Transmit-Only mode in the event of invalid activity on the I2C bus. The ST24FW21 differs from the ST24FC21 in having the write control input on pin 3.

Operating over a wide 3.6 - 5.5V supply voltage range and offered in 8-pin plastic DIP and SO packages, the expanded ST24xy21 family is aimed primarily at Plug & Play monitors and other PC peripherals but is also suitable for identifying any slave connected to the serial Plug & Play bus.

SGS-THOMSON Microelectronics is the world's number one manufacturer of programmable non-volatile memories, a classification that includes EEPROMs, EPROMs and flash memories.

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