Z8F640x/Z8F480x/Z8F320x/Z8F240x/Z8F160x
Z8 Encore!®
81
5. Check the TDREbit in the UART Status 0 register to determine if the Transmit Data
register is empty (indicated by a 1). If empty, continue to Step 6. If the Transmit Data
register is full (indicated by a 0), continue to monitor the TDREbit until the Transmit
Data register becomes available to receive new data.
6. Write the data byte to the UART Transmit Data register. The transmitter automatically
transfers the data to the Transmit Shift register and transmit the data.
7. To transmit additional bits, return to Step 5.
Transmitting Data using the Interrupt-Driven Method
The UART Transmitter interrupt indicates the availability of the Transmit Data register to
accept new data for transmission. Follow these steps to configure the UART for interrupt-
driven data transmission:
1. Write to the UART Baud Rate High and Low Byte registers to set the desired baud
rate.
2. Enable the UART pin functions by configuring the associated GPIO Port pins for
alternate function operation.
3. Execute a DI instruction to disable interrupts.
4. Write to the Interrupt control registers to enable the UART Transmitter interrupt and
set the desired priority.
5. Write to the UART Control 1 register to enable Multiprocessor (9-bit) mode functions,
if desired.
6. Write to the UART Control 0 register to:
–
–
–
Set the transmit enable bit (TEN) to enable the UART for data transmission
Enable parity, if desired, and select either even or odd parity.
Set or clear the CTSEbit to enable or disable control from the receiver via the
CTS pin.
7. Execute an EI instruction to enable interrupts.
The UART is now configured for interrupt-driven data transmission. When the UART
Transmit interrupt is detected, the associated interrupt service routine (ISR) should per-
form the following:
8. Write the data byte to the UART Transmit Data register. The transmitter will
automatically transfer the data to the Transmit Shift register and transmit the data.
9. Clear the UART Transmit interrupt bit in the applicable Interrupt Request register.
10. Execute the IRET instruction to return from the interrupt-service routine and wait for
the Transmit Data register to again become empty.
PS017610-0404
UART
ZILOG [ ZILOG, INC. ]
