Z8F6421PM020SC Datasheet, PDF (127/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
107
Receiver Interrupts
The receiver generates an interrupt when any of the following occurs:
• A data byte has been received and is available in the UART Receive Data register.
This interrupt can be disabled independent of the other receiver interrupt sources. The
received data interrupt occurs once the receive character has been received and placed
in the Receive Data register. Software must respond to this received data available
condition before the next character is completely received to avoid an overrun error.
Note that in multiprocessor mode (MPEN = 1), the receive data interrupts are
dependent on the multiprocessor configuration and the most recent address byte.
• A break is received
• An overrun is detected
• A data framing error is detected
UART Overrun Errors
When an overrun error condition occurs the UART prevents overwriting of the valid data
currently in the Receive Data register. The Break Detect and Overrun status bits are not
displayed until after the valid data has been read.
After the valid data has been read, the UART Status 0 register is updated to indicate the
overrun condition (and Break Detect, if applicable). The RDA bit is set to 1 to indicate that
the Receive Data register contains a data byte. However, because the overrun error
occurred, this byte may not contain valid data and should be ignored. The BRKD bit indi-
cates if the overrun was caused by a break condition on the line. After reading the status
byte indicating an overrun error, the Receive Data register must be read again to clear the
error bits is the UART Status 0 register. Updates to the Receive Data register occur only
when the next data word is received.
UART Data and Error Handling Procedure
Figure 18 illustrates the recommended procedure for use in UART receiver interrupt ser-
vice routines.
PS019915-1005
UART