Datasheet

Table Of Contents
Enhanced Serial Communications Interface (ESCI) Module
MC68HC908GR60A • MC68HC908GR48A • MC68HC908GR32A Data Sheet, Rev. 5
156 Freescale Semiconductor
13.4.2 Transmitter
Figure 13-5 shows the structure of the SCI transmitter and the registers are summarized in Figure 13-4.
The baud rate clock source for the ESCI can be selected via the configuration bit, SCIBDSRC.
Figure 13-5. ESCI Transmitter
13.4.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in ESCI control
register 1 (SCC1) determines character length. When transmitting 9-bit data, bit T8 in ESCI control
register 3 (SCC3) is the ninth bit (bit 8).
13.4.2.2 Character Transmission
During an ESCI transmission, the transmit shift register shifts a character out to the TxD pin. The ESCI
data register (SCDR) is the write-only buffer between the internal data bus and the transmit shift register.
PEN
PTY
H876543210L
11-BIT
TRANSMIT
STOP
START
T8
SCTE
SCTIE
TCIE
SBK
TC
PARITY
GENERATION
MSB
ESCI DATA REGISTER
LOAD FROM SCDR
SHIFT ENABLE
PREAMBLE
(ALL ONES)
BREAK
(ALL ZEROS)
TRANSMITTER
CONTROL LOGIC
SHIFT REGISTER
TC
SCTIE
TCIE
SCTE
M
ENSCI
LOOPS
TE
TXINV
INTERNAL BUS
÷ 4
PRE-
SCALER
SCP1
SCP0
SCR1
SCR2
SCR0
BAUD
DIVIDER
÷ 16
SCI_TxD
PRE-
SCALER
PDS1
PDS2
PDS0
PSSB3
PSSB4
PSSB2
PSSB1
PSSB0
LINT
TRANSMITTER CPU
INTERRUPT REQUEST
CGMXCLK
OR
BUS CLOCK