XR16C864
24
Rev. 1.10
the trigger level (if FIFO is enabled) and is associated
with bit-1 in the LSR register.
Logic 0 = Disable the transmitter empty interrupt.
(normal default condition)
Logic 1 = Enable the transmitter empty interrupt.
IER BIT-2:
This interrupt will be issued whenever a receive data
error condition exists as reflected in LSR bits 1-4.
Logic 0 = Disable the receiver line status interrupt.
(normal default condition)
Logic 1 = Enable the receiver line status interrupt.
IER BIT-3:
Logic 0 = Disable the modem status register interrupt.
(normal default condition)
Logic 1 = Enable the modem status register interrupt.
IER BIT -4:
Logic 0 = Disable sleep mode. (normal default condi-
tion)
Logic 1 = Enable sleep mode. See Sleep Mode section
for details.
IER BIT-5:
Logic 0 = Disable the software flow control, receive
Xoff interrupt. (normal default condition)
Logic 1 = Enable the software flow control, receive
Xoff interrupt. See Software Flow Control section for
details.
IER BIT-6:
Logic 0 = Disable the RTS interrupt. (normal default
condition)
Logic 1 = Enable the RTS interrupt. The 864 issues an
interrupt when the RTS pin transitions from a logic 0
to a logic 1.
IER BIT-7:
Logic 0 = Disable the CTS interrupt. (normal default
condition)
Logic 1 = Enable the CTS interrupt. The 864 issues an
interrupt when CTS pin transitions from a logic 0 to a
logic 1.
FIFO Control Register (FCR)
This register is used to enable the FIFO’s, clear the
FIFO’s, set the transmit/receive FIFO trigger levels, and
select the DMA mode. The DMA, and FIFO modes are
defined as follows:
DMA MODE
Mode 0
transmit or receive operation, and is similar to the
ST16C454 mode. Transmit Ready (-TXRDY) will go to a
logic 0 whenever the TX FIFO is empty. Receive Ready
(-RXRDY) will go to a logic 0 whenever the Receive
Holding Register (RHR) is loaded with a character.
Mode 1
Set and enable the interrupt in a block
mode operation. The transmit interrupt is set when the
transmit FIFO is below the programmed trigger level.
-TXRDY remains a logic 0 as long as one empty FIFO
location is available. The receive interrupt is set when
the receive FIFO fills to the programmed trigger level.
However the FIFO continues to fill regardless of the
programmed level until the FIFO is full. -RXRDY
remains a logic 0 as long as the FIFO fill level is above
the programmed trigger level.
Set and enable the interrupt for each single
FCR BIT-0:
Logic 0 = Disable the transmit and receive FIFO.
(normal default condition)
Logic 1 = Enable the transmit and receive FIFO. This
bit must be a “1” when other FCR bits are written to or
they will not be programmed.
FCR BIT-1:
Logic 0 = No FIFO receive reset. (normal default
condition)
Logic 1 = Clears the contents of the receive FIFO and
resets the FIFO counter logic (the receive shift regis-
ter is not cleared or altered).
FCR BIT-2:
Logic 0 = No FIFO transmit reset. (normal default
condition)
Logic 1 = Clears the contents of the transmit FIFO and
resets the FIFO counter logic (the transmit shift regis-
ter is not cleared or altered).
FCR BIT-3:
Logic 0 = Set DMA mode “0”. (normal default condition)
Logic 1 = Set DMA mode “1.”
Transmit operation n mode “0”:
When the 864 is in the ST16C450 mode (FIFO’s