Z8F6421PM020SC Datasheet, PDF (143/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
123
16-clock
period
Baud Rate
Clock
IR_RXD
Start Bit = 0
Data Bit 0 = 1 Data Bit 1 = 0 Data Bit 2 = 1 Data Bit 3 = 1
min. 1.6μs
pulse
UART’s
RXD
Start Bit = 0
Data Bit 0 = 1
8-clock
delay
16-clock
period
16-clock
period
Figure 21. Infrared Data Reception
Data Bit 1 = 0
16-clock
period
Data Bit 2 = 1
16-clock
period
Data Bit 3 = 1
Caution:
The system clock frequency must be at least 1.0MHz to ensure proper re-
ception of the 1.6μs minimum width pulses allowed by the IrDA standard.
Endec Receiver Synchronization
The IrDA receiver uses a local baud rate clock counter (0 to 15 clock periods) to generate
an input stream for the UART and to create a sampling window for detection of incoming
pulses. The generated UART input (UART RXD) is delayed by 8 baud rate clock periods
with respect to the incoming IrDA data stream. When a falling edge in the input data
stream is detected, the Endec counter is reset. When the count reaches a value of 8, the
UART RXD value is updated to reflect the value of the decoded data. When the count
reaches 12 baud clock periods, the sampling window for the next incoming pulse opens.
The window remains open until the count again reaches 8 (or in other words 24 baud clock
periods since the previous pulse was detected). This gives the Endec a sampling window
of minus four baudrate clocks to plus eight baudrate clocks around the expected time of an
incoming pulse. If an incoming pulse is detected inside this window this process is
repeated. If the incoming data is a logical 1 (no pulse), the Endec returns to the initial state
and waits for the next falling edge. As each falling edge is detected, the Endec clock
counter is reset, resynchronizing the Endec to the incoming signal. This action allows the
Endec to tolerate jitter and baud rate errors in the incoming data stream. Resynchronizing
the Endec does not alter the operation of the UART, which ultimately receives the data.
The UART is only synchronized to the incoming data stream when a Start bit is received.
PS019915-1005
Infrared Encoder/Decoder