xr16v554 Exar Corporation, xr16v554 Datasheet - Page 18

• Manufacturer Part Number: xr16v554
• Description: 2.25v To 3.6v Quad Uart With 16-byte Fifo
• Manufacturer: Exar Corporation

XR16V554/554D
2.25V TO 3.6V QUAD UART WITH 16-BYTE FIFO
The V554 UART provides an internal loopback capability for system diagnostic purposes. The internal
loopback mode is enabled by setting MCR register bit-4 to logic 1. All regular UART functions operate normally.
Figure 11
output is internally routed to the receive shift register input allowing the system to receive the same data that it
was sending. The TX pin is held HIGH or mark condition while RTS# and DTR# are de-asserted, and CTS#,
DSR# CD# and RI# inputs are ignored. Caution: the RX input must be held HIGH during loopback test else
upon exiting the loopback test the UART may detect and report a false “break” signal.
F
2.11
IGURE
11. I
Internal Loopback
shows how the modem port signals are re-configured. Transmit data from the transmit shift register
NTERNAL
L
OOPBACK
Transmit Shift Register
Receive Shift Register
(THR/FIFO)
(RHR/FIFO)
RTS#
CTS#
DTR#
DSR#
CD#
RI#
MCR bit-4=1
18
VCC
VCC
OP1#
OP2#
VCC
TX A-D
RX A-D
RTS# A-D
CTS# A-D
DTR# A-D
DSR# A-D
RI# A-D
CD# A-D
REV. 1.0.2