M48A-000-DIL RADIOMETRIX, M48A-000-DIL Datasheet - Page 8

• Manufacturer Part Number: M48A-000-DIL
• Description: IC, CONTROLLER, SERIAL MODEM, 20DIP
• Manufacturer: RADIOMETRIX

Specifications of M48A-000-DIL

• Baud Rate: 4800baud
• Supply Voltage Range: 4.5V To 5.5V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: DIP
• No. Of Pins: 20
• Controller Type: MOSFET
• Data Format: Asynchronous

This function output a data packet to the transmitter, then returns to setup mode.
The (length byte) is a single hex character. It sets the length of a transient data buffer,
The actual buffer length is one more than the value of the length byte, so 0-F corresponds to
a buffer between 1 and 16 bytes long
The (data string) is a string of bytes equal in number to (length+1)
After the length byte, the M48 sends back a colon character (ASCII 58)
When the final byte is received, the modem goes into transmit, and sends the packet.
By careful use of the & and $ command bytes, the M48 can be used in a non-transparent mode, without ever
leaving command mode. This is especially useful for the master node in point to multi-point operation.
Timings
The data throughput of the M48A is limited by the radio path. In continuously streaming (transparent) mode a
baud rate of 4800 baud is supported without any buffer overflows.
Byte latency is influenced by the switching performance of the radio (and the programmed DELAY and
PREAM values).
In default mode (20mS delay, 50mS preamble) the single byte in to out latency is of the order of 110mS
(20+50+40mS burst length and processing delays) although in streaming data this is reduced to around
30mS
If radio switching times are faster, then the preamble duration and the tx off delay can be reduced (crystal
controlled radios such as NiM2 work well with 15mS of preamble, 5mS tx off) and latency falls to around
40mS
In ANK mode, the switching speed of the radios, and the time absorbed in sending and decoding the
acknowledge burst dominate the data throughput. The acknowledge in itself requires only 20mS, but the
requirement to switch both radios between receive and transmit (to send the data packet, and then the akn
packet) adds a significant overhead.
Referring to the default timing setup this results in 1 packet per 150mS, and a peak data througput of only
900 baud, although if radios with faster switching performance are used then this is significantly increased.
(With NiM2 or BiM1 radios, the preamble duration can be significantly reduced, and an aknowledged mode
data rate of well over 1200 baud is achievable)
Unless only short data bursts are used, we recommend the use of CTS flow control if AKN is selected
Other versions
The basic part, described in this document, is the M48A. Other versions (with different default settings,
and/or different pin outs) are available :
Radiometrix Ltd
M48A Modem Data Sheet
page 8