
Technical Data
MC68HC11E Family
—
Rev. 4
152
Serial Communications Interface (SCI)
MOTOROLA
Serial Communications Interface (SCI)
7.8 SCI Registers
Five addressable registers are associated with the SCI:
Four control and status registers:
–
Serial communications control register 1 (SCCR1)
–
Serial communications control register 2 (SCCR2)
–
Baud rate register (BAUD)
–
Serial communications status register (SCSR)
One data register:
–
Serial communications data register (SCDR)
The SCI registers are the same for all M68HC11 E-series devices with
one exception. The SCI system for MC68HC(7)11E20 contains an extra
bit in the BAUD register that provides a greater selection of baud
prescaler rates. Refer to
7.8.5 Baud Rate Register
,
Figure 7-8
, and
Figure 7-9
.
7.8.1 Serial Communications Data Register
SCDR is a parallel register that performs two functions:
The receive data register when it is read
The transmit data register when it is written
Reads access the receive data buffer and writes access the transmit
data buffer. Receive and transmit are double buffered.
Address:
$102F
Bit 7
6
5
4
3
2
1
Bit 0
Read:
R7/T7
R6/T6
R5/T5
R4/T4
R3/T3
R2/T2
R1/T1
R0/T0
Write:
Reset:
Indetermnate after reset
Figure 7-3. Serial Communications Data Register (SCDR)