GRAK -- UART board

GRAK

UART Board

Parts cost:
Average current:

$37
25 ma

The GRAK UART board is built around a stand-alone Universal Asynchronous Receiver Transmitter chip. This chip takes an 8 bit parallel input and transforms it into a serial data stream. It also performs the inverse function and can decode a serial byte into 8 parallel bits. A level shifter is provided to convert the serial stream to the +/- 10 volt levels used by standard RS-232 interfaces. However, the raw 5 volt receive and transmit lines are also brought out to the edge connector and can be used directly if the level-shifter chip is removed.

The UART board normally operates in a "ping-pong" mode. For each byte the host computer sends down, the UART board automatically responds with a single byte. Alternatively, the transmit and receive functions can be directly controlled using the control lines provided. By adding a ribbon cable, the UART board can also be used to "engram" the NVRAM controller. A special download mode is initiated when the UART receives a "break" and is terminated automatically once 2048 bytes have been received.

Block Diagram

block diagram

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