ZLP12840 datasheet(58/58 Pages) ZILOG

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PS024406-0106

P R E L I M I N A R Y

Operation

ZLP12840 OTP MCU

Product Specification

Receiving Data Using the Polled Method

Follow these steps to configure the UART for polled data reception:

1. Write to the BCNST register to set the appropriate baud rate.

2. Write to the UART control register (UCTL) to:

a. Set the receive enable bit (UCTL[6]) to enable the UART for data reception

b. Enable parity, if appropriate and select either even or odd parity

3. Check the receive status bit in the UART Status register, bit UST[7], to determine if

the Receive Data register contains a valid data byte (indicated by a 1). If UST[7] is set

to 1 to indicate available data, continue to Step 4. If the Receive Data register is empty

(indicated by a 0), continue to monitor the UST[7] bit awaiting reception of the valid

data.

4. Read data from the UART Receive Data register.

5. Return to Step 3 to receive additional data.

Receiving Data Using the Interrupt-Driven Method

The UART Receiver interrupt indicates the availability of new data (as well as error condi-

tions). Follow these steps to configure the UART receiver for interrupt-driven operation:

1. Write to the UART BRG Constant registers to set the appropriate baud rate.

2. Execute a DI instruction to disable interrupts.

3. Write to the interrupt control registers to enable the UART receiver interrupt and set

the appropriate priority.

4. Clear the UART Receiver interrupt in the applicable Interrupt Request register.

5. Write to the UART Control register (UCTL) to:

a. Set the receive enable bit (UCTL[6]) to enable the UART for data reception

b. Enable parity, if appropriate, and select either even or odd parity

6. Execute an EI instruction to enable interrupts.

The UART is now configured for interrupt-driven data reception. When the UART

Receiver interrupt is detected, the associated interrupt service routine (ISR) performs the

following:

1. Checks the UART Status register to determine the source of the interrupt, whether it is

an error, break, or received data.

2. Reads the data from the UART Receive Data register if the interrupt was caused by

data available.

3. Clears the UART receiver interrupt in the applicable Interrupt Request register.

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