NanoBoard 3000 - Board ID Memory

Board identification is handled courtesy of a DS2502 1024-bit, 1-Wire EPROM device (from Maxim). The DS2502 is primarily used to contain a code with which to identify the motherboard. It is also used to contain additional information such as revision, release date, and so on. The Host (NanoTalk) Controller interrogates this device over a single wire, the associated signal of which is ONE_WIRE_ID.

1-Wire memory used to contain the
ident code for the board.

The DS2502 supports half-duplex communication at a rate of up to 16.3kbits/s. Although power for the device is sourced over the same single wire as the data itself – courtesy of a parasitic capacitor which charges when the 1-Wire bus signal line is High – the device is also fed from the motherboard's 3.3V supply, to ensure continuous power.

A similar 1-Wire memory device on an attached peripheral board allows the NanoTalk Controller to detect the specific hardware available to the system. This hardware detection provides the underlying mechanism for auto-configuration of an FPGA project.

Location on Board

The DS2502 device (designated U23) is located near the right edge on the component side of the board, to the right of the 'PWR' and 'PGM' LEDs, associated with the User FPGA.

Schematic Reference

The 1-Wire memory device can be found on Sheet 20 (1WB_DS2502_ID.SchDoc, entitled Protected 1-Wire EPROM) of the motherboard schematics.

Further Device Information

For more information on the DS2502 device, refer to the datasheet (DS2502.pdf) available at www.maxim-ic.com.