MC68HC908EY16 Datasheet, PDF (127/278 Pages) Motorola, Inc – Microcontrollers

Functional Description
13.4 Functional Description
Figure 13-2 shows the structure of the ESCI module. The ESCI allows full-duplex, asynchronous, NRZ
serial communication between the MCU and remote devices, including other MCUs. The transmitter and
receiver of the ESCI operate independently, although they use the same baud rate generator. During
normal operation, the CPU monitors the status of the ESCI, writes the data to be transmitted, and
processes received data.
The baud rate clock source for the ESCI can be selected via the configuration bit, ESCIBDSRC, of the
CONFIG2 register ($001E).
INTERNAL BUS
ESCI DATA
REGISTER
RxD
RECEIVE
SHIFT REGISTER
ESCI DATA
REGISTER
RxD
SCI_TxD
TRANSMIT
SHIFT REGISTER
ARBITER- TxD
BUS CLOCK
CGMXCLK
LINR
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
Enhanced
PRE-
SCALER
SL
TXINV
R8
T8
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
LOOPS
LOOPS
ENSCI
ORIE
NEIE
FEIE
PEIE
WAKEUP
CONTROL
RECEIVE
CONTROL
FLAG
CONTROL
TRANSMIT
CONTROL
BKF
ENSCI
RPF
÷4
PRE- BAUD RATE
SCALER GENERATOR
M
WAKE
ILTY
PEN
PTY
BUS_CLK
SL
ACLK bit in SCIACTL
÷ 16
DATA SELECTION
CONTROL
SL=1 -> SCI_CLK = BUSCLK
SL=0 -> SCI_CLK = CGMXCLK (4x BUSCLK)
Figure 13-2. ESCI Module Block Diagram
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
Freescale Semiconductor
127