X24-009PKC-RA Digi International/Maxstream, X24-009PKC-RA Datasheet - Page 47

• Manufacturer Part Number: X24-009PKC-RA
• Description: MOD RF 2.4GHZ 9600BPS RS232/485
• Manufacturer: Digi International/Maxstream
• Series: XStream™r

Specifications of X24-009PKC-RA

• Function: Transceiver, Modem
• Modulation Or Protocol: FHSS
• Frequency: 2.4GHz ~ 2.4835GHz
• Applications: General Purpose
• Interface: RS-232, RS-485
• Sensitivity: -110dBm
• Power - Output: 17dBm (50mW)
• Data Rate - Maximum: 20 kbps
• Voltage - Supply: 5V
• Package / Case: Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

XStream‐PKG‐R™ RS‐232/485 RF Modem – Product Manual v5.x00 [2006.02.24]
After receiving and acknowledging a packet, the receiving modem will move to the next
frequency and listen for either a retransmission or new data for a specific period of time. Even if
the transmitting modem has indicated that it has no more pending transmit data, it may have not
received the previous ACK, and so it may retransmit the packet (potentially with no delay after
the ACK slot). In this case, the receiving modem will always detect the immediate
retransmission, which will hold off the communications channel and thereby reduce collisions.
Receiving modems acknowledge each retransmission they receive, but they only pass the first
copy of a packet they receive out the UART.
RB and RO parameters are not applied to subsequent packets. This means that once transmission
has begun, it will continue uninterrupted until the DI buffer is empty or the streaming limit (TT)
has been reached. As with the first packet, the payload of each subsequent packet includes up to
the maximum packet size (PK parameter). The transmitting modem checks for more pending
data near the end of each packet.
The streaming limit (TT parameter) specifies the maximum number of bytes that the transmitting
modem will send in one transmission event, which may consist of many packets and retries. If
the TT parameter is reached, the transmitting modem will force a random delay of 1 to RN delay
slots (exactly 1 delay slot if RN is zero). Each packet is counted only once toward TT, no matter
how many times the packet is retransmitted.
Subsequent packets in acknowledged mode are similar to those in streaming mode, with the
addition of an acknowledgement between each packet, and the possibility of retransmissions.
Subsequent packets are sent without an RF initializer, as the receiving modems are already
synchronized to the transmitting modem from the preceding packet(s) and they remain
synchronized for the duration of the transmission event. Each retransmission of a packet includes
an RF initializer.
Once the transmitting modem has sent all pending data or has reached the TT limit, the
acknowledged transmission event is completed. The transmitting modem will not transmit again
for exactly RN delay slots, if the local RN parameter is set to a nonzero value. The receiving
modem will not transmit for a random number of delay slots between 0 and (RN-1), if the local
RN parameter is set to a nonzero value. These delays are intended to lessen congestion following
long bursts of packets from a single transmitting modem, during which several receiving modems
may have themselves become ready to transmit.
© 2006 MaxStream, Inc. Confidential & Proprietary
47