Rev. 3.0, 03/01, page 161 of 390
(3) UFCR (WRITE only)
This register is used to enable, clear the FIFO, and set the RCVR FIFO trigger levels.
Bit
Description
Default
7, 6
These bits set the trigger levels for the RCVR FIFO interrupt.
UFCR(7) UFCR(6) RCVR FIFO Trigger Level
0 0 1 byte
0 1 4 bytes
1 0 8 bytes
1 1 14 bytes
-
5, 4
Reserved
-
3
This bit doesn’t affect the Serial Channel operation. RXRDY and TXRDY functions are not
available on this controller.
-
2
This self-clearing bit clears all contents of the XMIT FIFO and resets its related counter to
0 by a logic “1”.
-
1
Setting this self-clearing bit to logic 1 clears all contents of the RCVR FIFO and resets its
related counter to 0 (except the shift register).
-
0
XMIT and RCVR FIFO are enabled when this bit is set high. XMIT and RCVR FIFO will be
disabled and cleared when this bit is cleared to low. This bit has to be a logic 1 if the other
bits of the UFCR are written to or they will not be properly programmed. When this
register changes to non-FIFO mode, all contents will be cleared.
-
(4) Divisor Latches (READ/WRITE)
There are two 8-bit Divisor Latches (UDLL and UDLM) which store the divisor in a 16-bit binary
format. They are loaded during initialization to generate a desired Baud Rate.
Baud Rate Generator (BRG)
Each serial channel contains a programmable BRG which can take any clock input (from DC to 8
MHz) to generate standard ANSI/CCITT bit rates for the channel clocking, with an external clock
oscillator. The UDLL or UDLM is a number of 16-bit format, providing the divisor range from 1
to 2
16
to obtain the desired baud rate. The output frequency is 16X data rate.
(5) Scratch Pad Register (READ/WRITE)
This 8-bit register does not control the operation of UART in any way. It is intended as a scratch
pad register to be used by programmer to temporarily hold general-purpose data.
Summary of Contents for HD64465
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