MC68HC08AZ16 Datasheet, PDF (179/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Serial Communications Interface Module (SCI)
• Transmission complete (TC) — The TC bit in SCS1 indicates that
the transmit shift register and the SCDR are empty and that no
break or idle character has been generated. The transmission
complete interrupt enable bit, TCIE, in SCC2 enables the TC bit to
generate transmitter CPU interrupt requests.
Receiver
MC68HC08AZ32
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Figure 3 shows the structure of the SCI receiver.
Character length
The receiver can accommodate either 8-bit or 9-bit data. The state of
the M bit in SCI control register 1 (SCC1) determines character
length. When receiving 9-bit data, bit R8 in SCI control register 2
(SCC2) is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a
copy of the eighth bit (bit 7).
Character reception
During an SCI reception, the receive shift register shifts characters in
from the PTE1/RxD pin. The SCI data register (SCDR) is the
read-only buffer between the internal data bus and the receive shift
register.
After a complete character shifts into the receive shift register, the
data portion of the character transfers to the SCDR. The SCI receiver
full bit, SCRF, in SCI status register 1 (SCS1) becomes set, indicating
that the received byte can be read. If the SCI receive interrupt enable
bit, SCRIE, in SCC2 is also set, the SCRF bit generates a receiver
CPU interrupt request or a receiver DMA service request.
The SCRF bit generates a receiver DMA service request if the DMA
receive enable bit, DMARE, in SCI control register 3 (SCC3) is set.
Setting the DMARE bit enables the SCRF bit to generate receiver
DMA service requests and disables receiver CPU interrupt requests.
Data sampling
The receiver samples the PTE1/RxD pin at the RT clock rate. The RT
clock is an internal signal with a frequency 16 times the baud rate. To
adjust for baud rate mismatch, the RT clock is resynchronized at the
following times (see Figure 4):
Serial Communications Interface Module (SCI)
10-sci
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