User`s guide

Targ et Preferences
read. If data is present, it reads and outputs the contents.
If no data is present, the system outputs the last value and
continues.
Character length bits
Length in bits of each transmitted/received character, set
to 8 bits.
Communication mode
Select
Raw_data or Protocol mode. Raw data is
unformatted and sent whenever the transmitting side is
ready to send, whether the receiving side is ready or not.
No deadlock condition can occur because there is no wait
state. Data transmission is asynchronous. W ith this mode,
it is possible the receiving side could miss data, b ut if the
data is noncritical, using raw data mode can avoid blocking
any processes.
When you specify protocol mode, some handshaking
between host and processo r occurs. The transmitting side
sends $SND to indicate that it is ready to transmit. T he
receiving side sends back $RD Y to indicate that it is ready
to receive. The transmitting side then sends data and, when
the transmission is completed, it sends a checksum.
Advantages to using protocol m ode include:
• Avoids deadlock
• Ensures that data is received correctly (checksum)
• Ensures that data is actually received by processor
• Ensures time consistency; each side waits for its turn to
send or receive
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