w65c51n Western Design Center, Inc., w65c51n Datasheet - Page 9

• Manufacturer Part Number: w65c51n
• Description: Asynchronous Communications Interface Adapter Acia
• Manufacturer: Western Design Center, Inc.

CONTROL REGISTER BIT DESCRIPTION
Selected Baud Rate (Bits 0, 1, 2, 3)
These bits select the Transmitter baud rate, which can be at 1/16 an external clock rate or one of 15 other
rates controlled by the internal baud rate generator.
If the Receiver clock uses the same baud rate at the transmitter, then RxC becomes an output and can
be used to slave other circuits to the ACIA. Figure 3 shows the Transmitter and Receiver layout.
Receiver Clock Source (Bit 4)
This bit controls the clock source to the Receiver. A 0 causes the Receiver to operate at a baud rate of
1/16 an external clock. A 1 causes the Receiver to operate at the same baud rate as is selected for the
transmitter.
Word Length (Bits 5, 6)
These bits determine the word length to be used (5, 6, 7 or 8 bits).
Stop Bit Number (Bit 7)
This bit determines the number of stop bits used. A 0 always indicates one stop bit. A 1 indicates 1½
stop bits if the word length is 5 with no parity selected 1 stop bit if the word length is 8 with parity selected
and 2 stop bits in all other configurations.
XTLO
XTLI
BAUD RATE
GENERATOR
BITS 0-3 IN
CONTROL
REGISTER
CONTROL
REGISTER
BIT 4
TRANSMITTER
SHIFT REGISTER
Figure 3 Transmitter/Receiver Clock Circuits
RECEIVER
SHIFT REGISTER
CLOCK
DIVIDER
(16)
CLOCK
DIVIDER
(16)
SYNC
LOGIC
RxD
RxC
TxD
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