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W83627UHG
Publication Release Date: March 24, 2008
-106-
Revision 1.44
10. UART PORT
10.1 Universal Asynchronous Receiver/Transmitter (UART A, B, C, D, E, F)
The UARTs are used to convert parallel data into serial format for transmission and to convert serial
data into parallel format during reception. The serial data format is a start bit, followed by five to eight
data bits, a parity bit (if programmed) and one, one-and-a-half (five-bit format only) or two stop bits.
The UARTs are capable of handling divisors of 1 to 65535 and producing a 16x clock for driving the
internal transmitter logic. Provisions are also included to use this 16x clock to drive the receiver logic.
The UARTs also support the MIDI data rate. Furthermore, the UARTs also include a complete
modem control capability and 16-byte FIFOs for reception and transmission to reduce the number of
interrupts presented to the CPU.
10.2 Register Address
10.2.1 UART Control Register (UCR) (Read/Write)
The UART Control Register defines and controls the protocol for asynchronous data communications,
including data length, stop bit, parity, and baud rate selection.
BIT
7
6
5
4
3
2
1
0
NAME
BDLAB
SSE
PBFE
EPE
PBE
MSBE
DLS1
DLS0
DEFAULT
0
BIT
DESCRIPTION
7
BDLAB (Baud Rate Divisor Latch Access Bit).
When this bit is set to logic 1, designers
can access the divisor (in 16-bit binary format) from the divisor latches of the baud-rate
generator during a read or write operation. When this bit is set to logic 0, the Receiver
Buffer Register, the Transmitter Buffer Register, and the Interrupt Control Register can be
accessed.
6
SSE (Set Silence Enable).
A logic 1 forces the Serial Output (SOUT) to a silent state (a
logical 0). Only IRTX is affected by this bit; the transmitter is not affected.
5
PBFE (Parity Bit Fixed Enable).
When PBE and PBFE of UCR are both set to logic 1,
(1) if EPE is logic 1, the parity bit is logical 0 when transmitting and checking;
(2) if EPE is logic 0, the parity bit is logical 1 when transmitting and checking.
4
EPE (Even Parity Enable).
When PBE is set to logic 1, this bit counts the number of logic
1’s in the data word bits and determines the parity bit. When this bit is set to logic 1, the
parity bit is set to logic 1 if an even number of logic 1’s are sent or checked. When the bit
is set to logic 0, the parity bit is logic 1, if an odd number of logic 1’s are sent or checked.
3
PBE (Parity Bit Enable).
When this bit is set to logic 1, the transmitter inserts a stop bit
between the last data bit and the stop bit of the SOUT, and the receiver checks the parity
bit in the same position.
2
MSBE (Multiple Stop Bit Enable).
Defines the number of stop bits in each serial
character that is transmitted or received.
(1) If MSBE is set to logic 0, one stop bit is sent and checked.