W90N745CD/W90N745CDG
UART3 Modem Status Register (UART3_MSR)
REGISTER
ADDRESS
R/W
DESCRIPTION
RESET VALUE
0xFFF8_0318
R
UART 3 Modem Status Register
0x0000_0000
UART3_MSR
31
23
15
7
30
22
14
6
29
21
13
5
28
20
12
4
27
19
11
3
26
18
10
2
25
17
9
24
16
8
Reserved
Reserved
Reserved
1
0
Reserved Reserved
DSR#
Reserved Reserved Reserved
DDSR
Reserved
Note: UART3_MSR is subset of MSR in W90N745. Please refer to section 7.10.5 ‘General UART Controller’.
6.10.5 General UART Controller
The Universal Asynchronous Receiver/Transmitter (UART) performs a serial-to-parallel conversion
on data characters received from the peripheral such as MODEM, and a parallel-to-serial conversion on
data characters received from the CPU. There are five types of interrupts, i.e., line status interrupt,
transmitter FIFO empty interrupt, receiver threshold level reaching interrupt, time out interrupt,
and MODEM status interrupt. One 16-byte transmitter FIFO (TX_FIFO) and one 16-byte (plus 3-bit of
error data per byte) receiver FIFO (RX_FIFO) has been built in to reduce the number of interrupts
presented to the CPU. The CPU can completely read the status of the UART at any time during the
operation. The reported status information includes the type and condition of the transfer operations
being performed by the UART, as well as any error conditions (parity, overrun, framing, or break
interrupt) found. The UART includes a programmable baud rate generator that is capable of dividing
crystal clock input by divisors to produce the clock that transmitter and receiver needed. The equation is
BaudOut = crystal clock / 16 * [Divisor + 2].
The UART includes the following features:
y
Transmitter and receiver are buffered with a 16-byte FIFO each to reduce the number of
interrupts presented to the CPU.
y
y
Subset of MODEM control functions (DSR, DTR, by IP selection)
Fully programmable serial-interface characteristics:
--
--
--
--
5-, 6-, 7-, or 8-bit character
Even, odd, or no-parity bit generation and detection
1-, 1&1/2, or 2-stop bit generation
Baud rate generation
Publication Release Date: September 22, 2006
Revision A2
- 261 -
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