Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 220)

Detailed Flowcharts
Appendix D
DĆ10
Figure D.11 shows the transmitter (XMIT) and receiver (RCVE) routines
sharing the transmit side of the UART. XMIT transmits messages and
inquiries. RCVE transmits responses. Therefore, each must wait until the
other is thru before it can transmit thru the UART. The TXALLOC and
TXFREE subroutines work together to ensure that XMIT and RVCE do
not try to use the UART at the same time. TXALLOC and TXFREE are
called in the SENDCTRL, SENDETX, and SENDDATA subroutines
(Figure D.12, Figure D.13, and Figure D.14).
Figure D.11
Sharing the Transmit Side of the UART
TXALLOC
UART Usage
TXFREE
XMIT RCVE
XMIT RCVE
Not–In–Use
Signal
10081–I
UART Sharing