MC68HC11PH8 Datasheet, PDF (93/264 Pages) Motorola, Inc – High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit

5
SERIAL COMMUNICATIONS INTERFACE^†
The serial communications interface (SCI) is a universal asynchronous receiver transmitter
(UART). It has a non-return to zero (NRZ) format (one start, eight or nine data, and one stop bit)
5
that is compatible with standard RS-232 systems.
The SCI shares I/O with two of port D’s pins:
Pin
Alternate
function
PD0
RXD1
PD1
TXD1
The SCI transmit and receive functions are enabled by TE and RE respectively, in SCCR2.
The SCI features enabled on this MCU include: 13-bit modulus prescaler, idle line detect,
receiver-active flag, transmitter and receiver hardware parity. A block diagram of the enhanced
baud rate generator is shown in Figure 5-1. See Table 5-1 for example baud rate control values.
ST4XCK
13-bit counter
Reset
13-bit compare ^EQ
SCBDH/L: SCI baud control
Internal
phase 2 clock
÷2
Sync
Transmitter
baud rate
clock
÷ 16
Receiver
baud rate
clock
Figure 5-1 SCI baud rate generator circuit diagram
† The MC68HC11PH8 contains two serial communications interfaces, both having similar
operation. For ease of reference, a full description of SCI1 (PD0/RXD1, PD1/TXD1) is given
first, followed by a summary of SCI2 (Section 5.8), detailing its differences.
MC68HC11PH8
SERIAL COMMUNICATIONS INTERFACE
TPG
MOTOROLA
5-1