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M2x40 Mote Datasheet Dust Networks™ 13
Table 13 Pin Usage
Pin Usage
RX, TX Used for serial data flow into and out of the mote.
MT_RTS
¯¯¯¯¯¯¯ This signal goes active low when the mote is ready to send a serial packet. The signal
stays low until the SP_CTS
¯¯¯¯¯¯¯
signal from the microprocessor goes active low (indicating
readiness to receive a packet) or the ack_delay timeout (see Error! Reference source
not found.) expires.
SP_CTS
SP_CTS
¯¯¯¯¯¯¯
should transition from high to active low in response to the MT_RTS
¯¯¯¯¯¯¯
signal from
the mote. This indicates that the microprocessor is ready to receive serial packets.
Following this, the microprocessor should strobe SP_CTS
¯¯¯¯¯¯¯
after receiving each byte. After
all packets are received, the microprocessor should de-assert the SP_CTS
¯¯¯¯¯¯¯
signal.
MT_CTS
¯¯¯¯¯¯¯
MT_CTS
¯¯¯¯¯¯¯
indicates the state of the network connection and availability of data buffers to
receive packets destined for the network. Once the mote has established wireless network
connection, it will use the MT_CTS
¯¯¯¯¯¯¯
pin to signify availability to accept serial packets for
wireless transmission. At certain critical times during communication, the mote may bring
MT_CTS
¯¯¯¯¯¯¯
high. MT_CTS
¯¯¯¯¯¯¯
will remain high if the mote does not have enough buffer space to
accept another packet. It will also remain high if the mote is not part of the network. OEM
designs must check that the MT_CTS
¯¯¯¯¯¯¯
pin is low before initiating each serial packet for
wireless transmission. Note that the mote may receive local serial packets at any time
regardless of the MT_CTS
¯¯¯¯¯¯¯
state.
Upon receipt of the first byte of the HDLC packet, the mote strobes MT_CTS
¯¯¯¯¯¯¯
in
acknowledgement of each subsequent byte. After the last byte of the packet is received,
MT_CTS
¯¯¯¯¯¯¯
switches back to signaling the availability of the network connection and data
buffers. The microprocessor should wait a minimum of interpacket_delay (see Error!
Reference source not found.) before initiating another packet transmission.
The mote can accept local commands (packets that are not sent through the network) at
any time, and the status of the MT_CTS
¯¯¯¯¯¯¯
pin may be ignored when initiating these packets.
(MT_CTS
¯¯¯¯¯¯¯
acknowledges each byte, as specified in section 8.3.2.1. For a list of local
commands,
see Mote Serial API guide.)
TIME
¯¯¯¯
The TIME
¯¯¯¯
pin is optional and can be used for triggering a timestamp packet. For details,
refer to 8.1.
8.3.2 Serial Interface Timing Requirements
8.3.2.1 CTS Byte-level Handshake
The following diagram shows generic CTS byte-level flow control timing. The following details are applicable to both
MT_CTS
¯¯¯¯¯¯¯
and SP_CTS
¯¯¯¯¯¯¯
.
Figure 8 CTS Byte-level Flow Control Timing