Chapter 12 Serial Communication Interface (S12SCIV6)
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
496
Freescale Semiconductor
12.4.5
Transmitter
Figure 12-16. Transmitter Block Diagram
12.4.5.1
Transmitter Character Length
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).
12.4.5.2
Character Transmission
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.
PE
PT
H
8
7
6
5
4
3
2
1
0
L
11-Bit Transmit Register
St
op
St
ar
t
T8
TIE
TDRE
TCIE
SBK
TC
Parity
Generation
MSB
SCI Data Registers
Load
from SCID
R
Shif
t Enable
P
rea
m
ble (
A
ll 1s
)
Brea
k (
A
ll 0s)
Transmitter Control
M
Internal Bus
SBR15:SBR4
Transmit baud
16
Bus
Clock
TE
SCTXD
TXPOL
LOOPS
LOOP
RSRC
CONTROL
To Receiver
Transmit
Collision Detect
TDRE IRQ
TC IRQ
SCTXD
SCRXD
(From Receiver)
TCIE
BERRIF
BER IRQ
BERRM[1:0]
generator
SBR3:SBR0
