MC68HC705C9A_1 Datasheet, PDF (90/157 Pages) Freescale Semiconductor, Inc – General Release Specification

Freescale Semiconductor, Inc.
General Release Specification _{Transmit Data Out (TDO)}
9.13 Transmit Data Out (TDO)
Transmit data is the serial data from the internal data bus that is applied
through the SCI to the output line. Data format is as discussed in 9.7
Data Format and shown in Figure 9-3. The transmitter generates a bit
time by using a derivative of the RT clock, thus producing a transmission
rate equal to 1/16th that of the receiver sample clock.
9.14 SCI I/O Registers
The following I/O registers control and monitor SCI operation:
• SCI data register (SCDR)
• SCI control register 1 (SCCR1)
• SCI control register 2 (SCCR2)
• SCI status register (SCSR)
9.14.1 SCI Data Register (SCDR)
The SCI data register, shown in Figure 9-8, is the buffer for characters
received and for characters transmitted.
$0011 Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
BIT7
BIT6 BIT55 BIT4
BIT3
BIT2
BIT1
BIT0
Reset:
Unaffected by Reset
Figure 9-8. SCI Data Register (SCDR)
9.14.2 SCI Control Register 1 (SCCR1)
The SCI control register 1, shown in Figure 9-9, has these functions:
• Stores ninth SCI data bit received and ninth SCI data bit
transmitted
• Controls SCI character length
• Controls SCI wakeup method
MC68HC705C9A — Rev. 2.0
Serial Communications Interface (SCI)
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