Manual

High-Speed Microcontroller User’s Guide
Rev: 062210 143 of 176
12.4 Serial I/O Description
A detailed description of each serial mode is given below. A description of framing error detection and
multiprocessor communication follows this section.
12.4.1 Mode 0
This mode is used to communicate in synchronous, half–duplex format with devices that accept the high-
speed microcontroller as a master. A functional block diagram and basic timing of this mode are shown in
Figure 12-1
. As can be seen, there is one bidirectional data line (RXD) and one shift clock line (TXD)
used for communication. The shift clock is used to shift data into and out of the microcontroller and the
remote device. Mode 0 requires that the microcontroller is the master because the microcontroller
generates the serial shift clocks for both directions. As described above, the shift clock may be selected to
be either divide-by-12 or divide-by-4 of the oscillator as determined by the SM2 (SCON0
.5 or SCON1.5)
bit.