xr17d152im Exar Corporation, xr17d152im Datasheet - Page 33

• Manufacturer Part Number: xr17d152im
• Description: Universal 3.3v And 5v Pci Bus Dual Uart
• Manufacturer: Exar Corporation

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REV. 1.2.0
Each UART channel provides an internal loopback capability for system diagnostic. The internal loopback
mode is enabled by setting MCR register bit-4 to logic 1. All regular UART functions operate normally.
Figure 18
output is internally routed to the receive shift register input allowing the system to receive the same data that it
was sending. The TX, RTS# and DTR# pins are held HIGH (idle or de-asserted state), and the CTS#, DSR#
CD# and RI# inputs are ignored.
The 2 sets of UART configuration registers are decoded using address lines A9 to A11 as shown below.
5.6
5.7
Internal Loopback
UART CHANNEL CONFIGURATION REGISTERS AND ADDRESS DECODING.
shows how the modem port signals are re-configured. Transmit data from the transmit shift register
F
IGURE
18. I
NTERNAL
L
OOP
A11
0
0
B
ACK
Transmit Shift
Receive Shift
F
A10
Register
Register
UNCTION IN EACH
0
0
A9
33
DTR#
DSR#
RTS#
CTS#
0
1
CD#
RI#
MCR bit-4=1
UNIVERSAL (3.3V AND 5V) PCI BUS DUAL UART
UART C
OP1#
OP2#
S
VCC
VCC
UART C
ELECTION
VCC
0
1
HANNEL
HANNEL
RX [1:0]
TX [1:0]
RTS# [1:0]
CTS# [1:0]
DTR# [1:0]
DSR# [1:0]
RI# [1:0]
CD# [1:0]
XR17D152