13.10.2 Transmitter Signals in Communication Modes
illustrates an example of transmitter signal timing that assumes the following conditions:
• Address-bit wake-up mode (address bit does not appear in idle-line mode)
• Three bits per character
Ad
TXENA
SCITXD pin
1
6
3
4
5
2
0
1
2
0
1
2
TXRDY
TX EMPTY
7
Start
Start
Stop
Stop
Ad
Pa
Pa
First Character
Second Character
Frame
Frame
Figure 13-9. SCI TX Signals in Communications Mode
Notes:
1. Bit TXENA (SCICTL1, bit 1) goes high, enabling the transmitter to send data.
2. SCITXBUF is written to; thus, (1) the transmitter is no longer empty, and (2) TXRDY goes low.
3. The SCI transfers data to the shift register (TXSHF). The transmitter is ready for a second character (TXRDY
goes high), and it requests an interrupt (to enable an interrupt, bit TX INT ENA — SCICTL2, bit 0 — must be
set).
4. The program writes a second character to SCITXBUF after TXRDY goes high (item 3). (TXRDY goes low
again after the second character is written to SCITXBUF.)
5. Transmission of the first character is complete. Transfer of the second character to shift register TXSHF
begins.
6. Bit TXENA goes low to disable the transmitter; the SCI finishes transmitting the current character.
7. Transmission of the second character is complete; transmitter is empty and ready for new character.
Serial Communications Interface (SCI)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
809
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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