xr16l2550im Exar Corporation, xr16l2550im Datasheet - Page 13

• Manufacturer Part Number: xr16l2550im
• Description: Industry Smallest Package Uart With 2.25v To 5.5v Operation
• Manufacturer: Exar Corporation

REV. 1.1.2
when data is not received for 4 word lengths as defined by LCR[1:0] plus 12 bits time. This is equivalent to 3.7-
4.6 character times. The RHR interrupt is enabled by IER bit-0.
The Receive Holding Register is an 8-bit register that holds a receive data byte from the Receive Shift
Register. It provides the receive data interface to the host processor. The RHR register is part of the receive
FIFO of 16 bytes by 11-bits wide, the 3 extra bits are for the 3 error tags to be reported in LSR register. When
the FIFO is enabled by FCR bit-0, the RHR contains the first data character received by the FIFO. After the
RHR is read, the next character byte is loaded into the RHR and the errors associated with the current data
byte are immediately updated in the LSR bits 2-4.
F
2.12.1
IGURE
Receive Data
Byte and Errors
10. R
16 bytes by 11-bit
16X Clock
Receive Holding Register (RHR) - Read-Only
F
ECEIVER
IGURE
wide
FIFO
16X Clock
and Errors
9. R
Data Byte
Receive
O
PERATION IN
ECEIVER
Receive Data Shift
Register (RSR)
O
Data FIFO
PERATION IN NON
LSR bits
Receive
Receive
FIFO
Tags in
Error
Data
4:2
Receive Data Shift
AND
Register (RSR)
Holding Register
Receive Data
A
FIFO Trigger=8
Data fills to 14
UTO
Data falls to 4
Validation
Data Bit
(RHR)
Example
-FIFO M
- RX FIFO trigger level selected at 8 bytes
RTS F
13
:
LOW
ODE
RTS# re-asserts when data falls below the flow
control trigger level to restart remote transmitter.
Enable by EFR bit-6=1, MCR bit-2.
RTS# de-asserts when data fills above the flow
control trigger level to suspend remote transmitter.
Enable by EFR bit-6=1, MCR bit-2.
Validation
LOW VOLTAGE DUART WITH 16-BYTE FIFO
Data Bit
RHR Interrupt (ISR bit-2) programmed for
desired FIFO trigger level.
FIFO is Enabled by FCR bit-0=1
C
ONTROL
RHR Interrupt (ISR bit-2)
M
Receive Data Characters
ODE
Receive Data Characters
RXFIFO1
XR16L2550
RXFIFO1