M48A-000-DIL RADIOMETRIX, M48A-000-DIL Datasheet - Page 6

• 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

of the data stream or uses the TX_flow signal.
This pin allows the status of the transmit buffer to be monitored. It begins low. It goes high when the buffer
reaches ¾ full, and is then re-set (to low) when the buffer is empty again.
It can be used to provide a simple 'CTS' signal.
[ It is possible to 'lose track' of the baud rate of a unit while manually programming it. In this case an easy
way of 'finding' the speed can be used: a byte should be sent to the device at each of the valid baud rates,
and the echoed character monitored. Only at the correct rate will a correct echo be seen ]
Timing commands
Note: Variables dd, pp and oo are all two digit hexadecimal values (00 to FF). These timing parameters are
immediately stored in E2PROM, and take effect right away.
The timing commands directly affect the way the modem device controls the radio module. Beware! If they
are set incorrectly then data errors or unreliable operation will result.
The default settings are a safe, conservative setup for a typical 50mS set-up time multi-channel transceiver.
For faster (usually single channel) radios the PREAM value can be reduced. Do not reduce this parameter
too far, as it must deal with the settling times of the receiver data recovery circuit as well as the transmitter
turn-on time.
The DELAY and TXOFF parameters are primarily concerned with optimum channel usage with intermittent
user data streams. DELAY is a duration between first byte received (into an empty buffer) and the
transmitter key-up, while TXOFF holds the transmitter on after a packet has finished sending.
If a user is controlling their serial data stream more closely, and sending data in discrete, well organised
bursts, then DELAY and TXOFF can be set to zero.
Addressing
The M48 data packet includes an address byte. It will only communicate with a unit set to the same address.
There are four receive addresses (of which ADR1 is usually set to zero as a 'broadcast' mode) and a
separate transmit address.
Multiple receive addresses can be useful for multiple node systems, and for setting up simple (manual
routing) repeater networks
Notes:
Mode commands
Beyond it's usual 'transparent data' mode, the M48 can also operate in an 'extended' mode. In this case the
maximum packet size is reduced from 16 bytes to 14, and a 'burst identifier' word is included (obviously this
slightly reduces overall throughput).
On transmit, a different burst identifier is attached to each new packet. The receiving unit ignores the second
(and subsequent) packet with the same identifier. This allows a receiving M48 to ignore multiple copies of
the same data packet (as will be encountered in multiple transmission or repeater/network systems)
Radiometrix Ltd
COMMANDS
DELAY dd
PREAM pp
TXOFF oo
COMMANDS
ADR1 aa
ADR2 aa
ADR3 aa
ADR4 aa
ADTX aa
ADDR aa
1. aa is a two digit hexadecimal value (00 to FE). Address FF (255) is not permitted.
2. Address commands write to volatile memory. To transfer programmed addresses to the power-up
3. As supplied: adr1 is zero, and adr2, adr3, adr4 and tx address are all set to 1.
settings, the PROM command must be used.
FUNCTION
Set the initial delay between first byte arrival and transmit start (20mS default)
Set the number of (620uS long) preamble bits (80 its / 50mS default)
Set the tx ramp-down period (20mS default)
FUNCTION
set receiver address 1
set receiver address 2
set receiver address 3
set receiver address 4
set transmitter address
set rx address 1 to zero and set tx address and rx addresses 2, 3 and 4 to a
M48A Modem Data Sheet
page 6