The synchronous interface exchanges 16-bit words. Eight bits are data, and the
other bits can hold status and control information. The chip can also send and
receive configuration data.
A crystal or ceramic resonator provides the timing reference for the UART??™s
bit-rate generator. A 1.8432MHz crystal supports bit rates from 300 to
115,200.
On receiving synchronous data to transmit, the MAX3100 writes a Start bit,
the data bits, a parity bit if used, and a Stop bit to TX. The data can have 7 or 8
bits plus an optional parity bit. The MAX3100 doesn??™t calculate a value for a
parity bit so the sending device must set the parity as desired. The Max3100
can generate an interrupt request on receiving a parity bit of 1.
Figure 11-2: The MAX3100 converts between SPI or Microwire serial data and
asynchronous format.
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The chip has an 8-byte FIFO for each direction, so the microcontroller or other
CPU doesn??™t have to read each received byte from the UART before the next
byte arrives.
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12
, &
When three or more devices share a communication path, serial-port programming
becomes more complicated. Each computer, or node, in the network,
needs to know when it??™s OK to transmit and whether to respond to or ignore a
received message. This chapter shows how to ensure reliable and efficient communications
in a serial network and how to implement a basic network protocol.
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