Rainbow Electronics W90N745CDG - Manual (Page 266)

W90N745CD/W90N745CDG
Publication Release Date: September 22, 2006
- 261 - Revision A2
UART3 Modem Status Register (UART3_MSR)
REGISTER ADDRESS R/W DESCRIPTION RESET VALUE
UART3_MSR 0xFFF8_0318 R UART 3 Modem Status Register 0x0000_0000
31 30 29 28 27 26 25 24
Reserved
23 22 21 20 19 18 17 16
Reserved
15 14 13 12 11 10 9 8
Reserved
7 6 5 4 3 2 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 Subset of MODEM control functions (DSR, DTR, by IP selection)
y 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