Hardware Interface; Pin Descriptions - Laird RM024 Hardware Integration Manual

RM024 Hardware Integration Guide
Version 3.1
H I
ARDWARE NTERFACE

Pin Descriptions

RXD and TXD
The RM024 accepts 3.3 VDC TTL level asynchronous serial data from the OEM host via the RXD
pin. Data is sent from the transceiver, at 3.3 V levels, to the OEM host via the TXD pin. Pins should
be left floating or high when not in use. Leaving the RXD tied low results in the radio transmitting
garbage serial data across the RF.
Force 9600 /Sleep Interrupt
When pulled logic Low before applying power or resetting, the transceiver's serial interface is
forced to 9600, 8-N-1 (8 data bits, No parity, 1 stop bit): regardless of the actual EEPROM setting.
RTS is ignored, the interface timeout is also set to 3 ms and the RF packet size is set to the default
size for the selected RF data rate. To exit, the transceiver must be reset or power-cycled with the
test pin logic High or disconnected. When in Force 9600 mode, the radio's receiver is disabled.
When enabled in the EEPROM, 9600 Boot option causes the 9600 pin to be ignored on cold boot
(power-up), command boot (0xCC 0xFF), and brown-out conditions. Therefore, the 9600 pin is
only observed on warm boots (reset pin toggled). This can be helpful so that brown-out
conditions don't cause the baud rate to change if the 9600 pin happens to be low at the time.
When 9600 Boot option is disabled, the 9600 pin is used for all boot conditions. 9600 Boot option is
enabled by default.
Force 9600 is also used to wake the radio from sleep. When the pin is taken low, the radio wakes.
The transceiver does not sleep if the pin is low when the sleep command is issued.
Note: Because this pin disables some modes of operation, it should not be permanently
pulled low during normal operation.
µP_RESET
µP_Reset provides a direct connection to the reset pin on the RM024 microprocessor and is
used to force a hard reset. For a valid reset, reset must be asserted Low for an absolute minimum
of 250 ns.
Command/Data
When logic High, the transceiver interprets incoming serial data as transmit data to be sent to
other transceivers. When logic Low, the transceiver interprets incoming serial data as command
data. When logic Low, data packets from the radio are not transmitted over the RF interface,
however, incoming packets from other radios are still received. Enabling CMD/Data RX Disable
in the EEPROM causes incoming RF packets to be queued by the receiving radio while
CMD/Data is low. When CMD/Data goes high, the data is sent over the serial interface.
In_Range
The In_Range pin is driven low when a client radio's frequency hopping is synchronized with that
of a server. In_Range is always driven low on a server. Following boot, In_Range transitions low in
approximately 12 ms on a server. For a client, the In_Range takes an average of 500 ms; this time
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