Serial Communications Interface (SCI)
Data Sheet
MC68HC908SR12MC68HC08SR12 — Rev. 5.0
252
Serial Communications Interface (SCI)
Freescale Semiconductor
16.8.2
RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273
16.9
16.9.1
16.9.2
16.9.3
16.9.4
16.9.5
16.9.6
16.9.7
I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .273
SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .273
SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .276
SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . .279
SCI Status Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .282
SCI Status Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .286
SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .287
SCI Baud Rate Register. . . . . . . . . . . . . . . . . . . . . . . . . . .288
16.2 Introduction
This section describes the serial communications interface (SCI)
module, which allows high-speed asynchronous communications with
peripheral devices and other MCUs.
NOTE:
When the SCI is enabled, the TxD pin is an open-drain output and
requires a pullup resistor to be connected for proper SCI operation.
NOTE:
References to DMA (direct-memory access) and associated functions
are only valid if the MCU has a DMA module. This MCU does not have
the DMA function. Any DMA-related register bits should be left in their
reset state for normal MCU operation.
16.3 Features
Features of the SCI module include the following:
Full-duplex operation
Standard mark/space non-return-to-zero (NRZ) format
32 programmable baud rates
Programmable 8-bit or 9-bit character length
Separately enabled transmitter and receiver
Separate receiver and transmitter CPU interrupt requests
Programmable transmitter output polarity