xr16l784iv Exar Corporation, xr16l784iv Datasheet - Page 39

• Manufacturer Part Number: xr16l784iv
• Description: High Performance 2.97v To 5.5v Quad Uart
• Manufacturer: Exar Corporation

xr
REV. 1.2.2
EFR[5]: Special Character Detect Enable
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EFR[6]: Auto RTS or DTR Flow Control Enable
RTS#/DTR# output may be used for hardware flow control by setting EFR bit-6 to logic 1. When Auto RTS/
DTR is selected, an interrupt will be generated when the receive FIFO is filled to the programmed trigger level
and RTS/DTR# will de-assert (HIGH) at the next upper trigger or selected hysteresis level. RTS/DTR# will re-
assert (LOW) when FIFO data falls below the next lower trigger or selected hysteresis level (see FCTR bits 4-
7). The RTS# or DTR# output must be asserted (LOW) before the auto RTS/DTR can take effect. The selection
for RTS# or DTR# is through MCR bit-2. RTS/DTR# pin will function as a general purpose output when
hardware flow control is disabled.
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EFR[7]: Auto CTS Flow Control Enable
Automatic CTS or DSR Flow Control.
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Transmit FIFO level byte count from 0x00 (zero) to 0x40 (64). This 8-bit register gives an indication of the
number of characters in the transmit FIFO. The FIFO level Byte count register is read only. The user can take
advantage of the FIFO level byte counter for faster data loading to the transmit FIFO., which reduces CPU
bandwidth requirements.
An 8-bit value written to this register sets the TX FIFO trigger level from 0x00 (zero) to 0x40 (64). The TX FIFO
trigger level generates an interrupt whenever the data level in the transmit FIFO falls below this preset trigger
level.
Receive FIFO level byte count from 0x00 (zero) to 0x40 (64). It gives an indication of the number of characters
in the receive FIFO. The FIFO level byte count register is read only. The user can take advantage of the FIFO
level byte counter for faster data unloading from the receiver FIFO, which reduces CPU bandwidth
requirements.
An 8-bit value written to this register, sets the RX FIFO trigger level from 0x00 (zero) to 0x40 (64). The RX
FIFO trigger level generates an interrupt whenever the receive FIFO level rises to this preset trigger level.
4.14
4.15
4.16
4.17
Logic 0 = Special Character Detect Disabled (default).
Logic 1 = Special Character Detect Enabled. The UART compares each incoming receive character with
data in Xoff-2 register. If a match exists, the received data will be transferred to FIFO and ISR bit-4 will be set
to indicate detection of the special character. Bit-0 corresponds with the LSB bit for the receive character. If
flow control is set for comparing Xon1, Xoff1 (EFR [1:0]=10) then flow control and special character work
normally. However, if flow control is set for comparing Xon2, Xoff2 (EFR[1:0]=01) then flow control works
normally, but Xoff2 will not go to the FIFO, and will generate an Xoff interrupt and a special character
interrupt.
Logic 0 = Automatic RTS/DTR flow control is disabled (default).
Logic 1 = Enable Automatic RTS/DTR flow control.
Logic 0 = Automatic CTS/DSR flow control is disabled (default).
Logic 1 = Enable Automatic CTS/DSR flow control. Transmission stops when CTS/DSR# pin de-asserts
(HIGH). Transmission resumes when CTS/DSR# pin is asserted (LOW). The selection for CTS# or DSR# is
through MCR bit-2.
TXCNT[7:0]: Transmit FIFO Level Counter - Read Only
TXTRG [7:0]: Transmit FIFO Trigger Level - Write Only
RXCNT[7:0]: Receive FIFO Level Counter - Read Only
RXTRG[7:0]: Receive FIFO Trigger Level - Write Only
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HIGH PERFORMANCE 2.97V TO 5.5V QUAD UART
XR16L784