mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 497

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

11.4.5
11.4.5.1
The SCI transmitter can accommodate either 8-bit or 9-bit data characters. The state of the M bit in SCI
control register 1 (SCICR1) determines the length of data characters. When transmitting 9-bit data, bit T8
in SCI data register high (SCIDRH) is the ninth bit (bit 8).
11.4.5.2
To transmit data, the MCU writes the data bits to the SCI data registers (SCIDRH/SCIDRL), which in turn
are transferred to the transmitter shift register. The transmit shift register then shifts a frame out through
the TXD pin, after it has prefaced them with a start bit and appended them with a stop bit. The SCI data
registers (SCIDRH and SCIDRL) are the write-only buffers between the internal data bus and the transmit
shift register.
Freescale Semiconductor
TDRE IRQ
BER IRQ
TC IRQ
Clock
Bus
SBR12:SBR0
Transmitter
Transmitter Character Length
Character Transmission
Baud Divider
PE
PT
M
Generation
Parity
T8
16
Figure 11-16. Transmitter Block Diagram
BERRIF
TDRE
TCIE
TCIE
MC9S12XDP512 Data Sheet, Rev. 2.17
TIE
TC
H
8
7
11-Bit Transmit Register
6
5
SCI Data Registers
4
Internal Bus
Transmitter Control
TE
3
2
Chapter 11 Serial Communication Interface (S12SCIV5)
Collision Detect
SBK
1
Transmit
0
BERRM[1:0]
L
TXPOL
CONTROL
LOOP
SCTXD
SCRXD
(From Receiver)
LOOPS
RSRC
To Receiver
SCTXD
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