Architecture; User Manual - Philips LPC2101 User Manual

Philips Semiconductors
Volume 1
Table 116: UART1 Transmit Enable Register (U1TER - address 0xE001 0030) bit description
Bit
6:0
7

10.4 Architecture

The architecture of the UART1 is shown below in the block diagram.
The APB interface provides a communications link between the CPU or host and the
UART1.
The UART1 receiver block, U1RX, monitors the serial input line, RXD1, for valid input. The
UART1 RX Shift Register (U1RSR) accepts valid characters via RXD1. After a valid
character is assembled in the U1RSR, it is passed to the UART1 RX Buffer Register FIFO
to await access by the CPU or host via the generic host interface.
The UART1 transmitter block, U1TX, accepts data written by the CPU or host and buffers
the data in the UART1 TX Holding Register FIFO (U1THR). The UART1 TX Shift Register
(U1TSR) reads the data stored in the U1THR and assembles the data to transmit via the
serial output pin, TXD1.
The UART1 Baud Rate Generator block, U1BRG, generates the timing enables used by
the UART1 TX block. The U1BRG clock input source is the APB clock (PCLK). The main
clock is divided down per the divisor specified in the U1DLL and U1DLM registers. This
divided down clock is a 16x oversample clock, NBAUDOUT.
The modem interface contains registers U1MCR and U1MSR. This interface is
responsible for handshaking between a modem peripheral and the UART1.
The interrupt interface contains registers U1IER and U1IIR. The interrupt interface
receives several one clock wide enables from the U1TX and U1RX blocks.
Status information from the U1TX and U1RX is stored in the U1LSR. Control information
for the U1TX and U1RX is stored in the U1LCR.

User manual

Symbol Description
- Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
TXEN When this bit is 1, as it is after a Reset, data written to the THR
is output on the TXD pin as soon as any preceding data has
been sent. If this bit cleared to 0 while a character is being sent,
the transmission of that character is completed, but no further
characters are sent until this bit is set again. In other words, a 0
in this bit blocks the transfer of characters from the THR or TX
FIFO into the transmit shift register. Software can clear this bit
when it detects that the a hardware-handshaking TX-permit
signal CTS has gone false, or it can clear this bit with software
handshaking, when it receives an XOFF character (DC3).
Software can set this bit again when it detects that the
TX-permit signal has gone true, or when it receives an XON
(DC1) character.
Rev. 01 — 12 January 2006
UM10161
Chapter 10: UART1
Reset value
NA
1
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
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