MC9S08GB60 Datasheet, PDF (170/290 Pages) Motorola, Inc – Microcontrollers

Serial Communications Interface (SCI) Module
The MC9S08GB/GT re-synchronizes to bit boundaries on every high-to-low transition, but in the worst
case, there are no such transitions in the full 10- or 11-bit time character frame so any mismatch in baud
rate is accumulated for the whole character time. For a Freescale Semiconductor SCI system whose bus
frequency is driven by a crystal, the allowed baud rate mismatch is about ±4.5 percent for 8-bit data format
and about ±4 percent for 9-bit data format. Although baud rate modulo divider settings do not always
produce baud rates that exactly match standard rates, it is normally possible to get within a few percent,
which is acceptable for reliable communications.
11.5 Transmitter Functional Description
This section describes the overall block diagram for the SCI transmitter, as well as specialized functions
for sending break and idle characters.
11.5.1 Transmitter Block Diagram
Figure 11-3 shows the transmitter portion of the SCI.
MC9S08GB/GT Data Sheet, Rev. 2.3
170
Freescale Semiconductor