Data Sheet

ISM14585-L35 Specification
DOC-DS-14585-201807-3.0
Confidential Inventek Systems
Page 50
An additional parity bit may be added to the serial character. This bit appears after the
last data bit and before the stop bit(s) in the character structure to provide the UART
with the ability to perform simple error checking on the received data.
The UART Line Control Register (UART_LCR_REG) is used to control the serial
character characteristics. The individual bits of the data word are sent after the start bit,
starting with the least significant bit (LSB). These are followed by the optional parity bit,
followed by the stop bit(s), which can be 1, 1.5 or 2.
All the bits in the transmission (with exception to the half stop bit when 1.5 stop bits are
used) are transmitted for exactly the same time duration. This is referred to as a Bit
Period or Bit Time. One BitTime equals 16 baud clocks. To ensure stability on the line
the receiver samples the serial input data at approximately the mid-point of the Bit Time
once the start bit has been detected. As the exact number of baud clocks that each bit
was transmitted for is known, calculating the mid-point for sampling is not difficult, that is
every 16 baud clocks after the mid-point sample of the start bit. Figure 22 shows the
sampling points of the first couple of bits in a serial character.
Figure 22 Receiver Serial Data Sampling Points
As part of the 16550 standard an optional baud clock reference output signal
(baudout_n) is supplied to provide timing information to receiving devices that require it.
The baud rate of the UART is controlled by the serial clock (sclk or pclk in a single clock
implementation) and the Divisor Latch Register (DLH and DLL).
9.8.2 IRDA 1.0 SIR PROTOCOL
The Infrared Data Association (IrDA) 1.0 Serial Infrared (SIR) mode supports
bidirectional data communications with remote devices using infrared radiation as the
transmission medium. IrDA 1.0 SIR mode specifies a maximum baud rate of 115.2kBd.
Note: Information provided on IrDA SIR mode in this section assumes that the reader is
fully familiar with the IrDA Serial Infrared Physical Layer Specifications. This
specification can be obtained from the following website: http://www.irda.org.