MC68HC08AS32 Datasheet, PDF (160/280 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

The SCI transmitter empty bit, SCTE in the SCI status control register (SCS1),
becomes set when the SCDR transfers a byte to the transmit shift register. The
SCTE bit indicates that the SCDR can accept new data from the internal data bus.
If the SCI transmit interrupt enable bit, SCTIE (SCC2), is also set, the SCTE bit
generates a transmitter CPU interrupt request.
When the transmit shift register is not transmitting a character, the PTE0/TxD pin
goes to the idle condition, logic 1. If at any time software clears the ENSCI bit in
SCI control register 1 (SCC1), the transmitter and receiver relinquish control of the
port E pins.
INTERNAL BUS
÷4
SCP1
SCP0
SCR1
SCR2
SCR0
PRE-
BAUD
SCALER DIVIDER
÷ 16
TXINV
SCI DATA REGISTER
11-BIT
TRANSMIT
SHIFT REGISTER
H876543210L
M
PEN
PARITY
PTY
GENERATION
T8
TRANSMITTER
CONTROL LOGIC
SCTE
SCTIE
TC
TCIE
SCTE
SCTIE
TC
TCIE
Figure 12-5. SCI Transmitter
SBK
LOOPS
ENSCI
TE
PTE0/TxD
Data Sheet
160
MC68HC08AS32 — Rev. 4.1
Freescale Semiconductor