8.16.2.2 4-Wire UART Topology
The 4-wire UART topology eliminates the host IRQ line (see
). Using this topology requires one of the
following conditions to be met:
• Host is always awake or active.
• Host goes to sleep, but the UART module has receiver start-edge detection for automatic wake up and does
not lose data.
HOST MCU
UART
CC3135MOD
UART
nRTS
nCTS
TX
RX
HOST_INTR(IRQ)
nRTS
nCTS
TX
RX
HOST_INTR(IRQ)
Figure 8-11. 4-Wire UART Configuration
8.16.2.3 3-Wire UART Topology
The 3-wire UART topology requires only the following lines (see
).
• RX
• TX
• nCTS
HOST MCU
UART
CC3135MOD
UART
nRTS
nCTS
TX
RX
HOST_INTR(IRQ)
nRTS
nCTS
TX
RX
HOST_INTR(IRQ)
Figure 8-12. 3-Wire UART Topology
Using 3-wire topology requires one of the following conditions to be met:
• Host always stays awake or active.
• Host goes to sleep, but the UART module has receiver start-edge detection for auto wake up and does not
lose data.
• Host can always receive any amount of data transmitted by the SimpleLink device because there is no flow
control in this direction.
Because there is no full flow control, the host cannot stop the SimpleLink device to send its data; thus, the
following parameters must be carefully considered:
• Maximum baud rate
• RX character interrupt latency and low-level driver jitter buffer
• Time consumed by the user's application
SWRS225D – FEBRUARY 2019 – REVISED MAY 2021
Copyright © 2021 Texas Instruments Incorporated
31