xr16m670 Exar Corporation, xr16m670 Datasheet - Page 22

• Manufacturer Part Number: xr16m670
• Description: 1.62v To 3.63v High Performance Uart With 32-byte Fifo
• Manufacturer: Exar Corporation

XR16M670
1.62V TO 3.63V HIGH PERFORMANCE UART WITH 32-BYTE FIFO
The M670 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.
register 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
2.18
IGURE
14. I
Internal Loopback
Figure 14
NTERNAL
shows how the modem port signals are re-configured. Transmit data from the transmit shift
L
OOPBACK
T ra n s m it S h ift R e g is te r
R e c e iv e S h ift R e g is te r
(R H R /F IF O )
(T H R /F IF O )
22
R T S #
C T S #
D T R #
D S R #
C D #
R I#
M C R b it-4 = 1
V C C
O P 2 #
O P 1 #
V C C
V C C
T X
R X
R T S #
C T S #
D T R #
D S R #
R I#
C D #
REV. 1.0.0