implemented. Although not every signal is explicitly referenced to UART 1 it is
nevertheless implicit.
All of the signals shown in the table above as
required need appropriate hardware
connectivity and software support in the Host application.
Figure 1.
Typical Host – Wireless CPU® UART1 interface
2.1.2
UART Signals Required for Implementing Sleep Control
Data is transmitted serially between the Host and Wireless CPU®’s UARTs using data
lines. From the Wireless CPU®’s perspective there is a receive (data from the Host to
the Wireless CPU®) and a transmit (data from the Wireless CPU® to the Host) which
operate asynchronously at the same baud rate in a full-duplex method of data
exchange. Similarly, these signals are present in the Host’s UART. Because of the
confusion which exists when referring to these (identical) signals at both ends of the
interface, the GR/GS64 uses a signal naming convention to identify their purpose in
relation to the Wireless CPU®; data-to-Wireless CPU® (receive) and data-from-
Wireless CPU® (transmit). In a practical implementation of a UART, these are the only
mandatory signals required since these carry the information (commands, responses,
data packets, status, etc.), the primary function of the interface. However, additional
hardware flow-control is necessary to activate and manage the sleep function of the
GR/GS64 products.
Basic flow-control, the regulation of data back and forth, is often necessary to
regulate the rate and volume of data being exchanged, so as to allow processing of
the information and to avoid over-filling the data buffers. Flow-control can be
implemented through a special protocol embedded in the data itself (software flow
control). In the GR/GS64 hardware flow-control is provided by the request-to-send
(RTS) and clear-to-send (CTS) handshaking between the UART interfaces. These
signals are required for sleep control.
APPLICATION NOTE
GR/GS64 UART Sleep Protocols
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