Peripheral Board ID Memory
Board identification is handled courtesy of a DS2406 device (from Dallas Semiconductor). Although the device is actually a dual-addressable switch, it is used for the additional 1kbit of memory that it possesses.
Figure 1. Example 1-Wire memory
device used to contain the ident
code for the board.
The DS2406 is a 1-Wire® compatible device, primarily used to contain a code with which to identify the peripheral board when plugged in. The NanoTalk Controller interrogates this device over a single wire, the associated signal of which depends on where the peripheral board is attached:
ONE_WIRE_PB_IDA– if attached to the'PERIPHERAL BOARD A'connector.
ONE_WIRE_PB_IDB– if attached to the'PERIPHERAL BOARD B'connector.
ONE_WIRE_PB_IDC– if attached to the'PERIPHERAL BOARD C'connector.
Some peripheral boards (e.g. PB01 – the Audio / Video Peripheral Board) are twice the width of other available peripheral boards and, as such, can only be connected to the NB2DSK01 using the 'PERIPHERAL BOARD A' or 'PERIPHERAL BOARD C' connectors.
The DS2406 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 peripheral board's 3.3V supply, to ensure continuous power.
Similar devices on all peripheral boards and 3-connector daughter boards allow the NanoTalk Controller to detect which specific boards are available to the system.
Location on Board
The DS2406 device (designated U1_ID) is located on the solder side of the board, to the bottom-left of the 100-way docking connector.
On the PB01 Audio / Video peripheral board, the DS2406 device is designated U1 and is located on the component side of the board, to the bottom-right of the CS4270 audio CODEC device (U1AC).
Schematic Reference
The 1-Wire memory device can be found on sheet 1WB_DS2406_EPROM.SchDoc (entitled 1-Wire Bus ID) of the peripheral board schematics.
Further Device Information
For more information on the DS2406 device, refer to the datasheet (DS2406.pdf) available at www.maxim-ic.com.