RFW-D100 Vishay, RFW-D100 Datasheet - Page 9

• Manufacturer Part Number: RFW-D100
• Manufacturer: Vishay

Specifications of RFW-D100

• Operating Temperature (min): 0C
• Operating Temperature (max): 70C
• Operating Temperature Classification: Commercial
• Package Type: LQFP
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (max): 3.6V
• Lead Free Status / Rohs Status: Supplier Unconfirmed

IDLE MODE
In idle mode, the RFW-D100 internally blocks the clock
input. The external clock is not stopped, but it is not
routed to the internal logic. By doing this, the MCU
achieves substantial power savings, and yet the
wakeup time is still relatively short. The power
consumption is not minimal since the external clock is
still active.
All registers and FIFOs retain their values when the
RFW-D100 is in idle mode.
The
IDLE_MODE pin to “0”. SYSTEM_CLOCK pin does
not output the oscillator clock.
The RFW-D100 goes back to working mode by setting
the IDLE_MODE pin to “1”.
Since the RFW-D100 retains all the registers’ values in
idle mode, special care should be given to the
registers’ values before the RFW-D100 enters idle
mode. For example, the MCU should check that the
RFW-D100 is not in the middle of transmitting or
receiving a packet. In addition, the RFACTIVE should
be set low, in order to shut down the RFW122.
PREAMBLE CORRELATION
The transmitting RFW-D100 sends the PREAMBLE in
order to synchronize the receiver with its transmission.
The RFW-D100 transmits a fixed size PREAMBLE of
20 bits. The first 4 bits are “1111”. Their purpose is to
initiate the RFW122 on the receiver side. The other 16
bits are determined by PRE-L and PRE-H. They are
transmitted from MSB to LSB.
The received PREAMBLE has a variable length of
16 ⇔ 9 bits, determined by SCR2 [5:7]. The receiver
correlates the 16 ⇔ 9 bits from its PRE-L and PRE-H
registers to the 16 ⇔ 9 bits in its input shift-register. If
a correlation was found, then the RFW-D100’s
receiver state machine is enabled.
The purpose of the PREAMBLE is to filter RFWaves
packets from white noise or other transmissions on the
channel. Whereas, NODE_ID and NET_ID filters are
used to filter packets from other RFWaves networks
(see section 0).
The PREAMBLE is transmitted MSB to LSB (PRE-H
first and then PRE-L).
The value of the PREAMBLE is determined according
to PRE-L and PRE-H registers for both the transmitter
and the receiver.
The value of the PRE-L and PRE-H registers should
be identical in the RFW-D100 in all nodes in the same
network.
Document Number 84675
Rev. 1.1, 22-Jan-07
RFW-D100
enters
idle
For more information please contact: [e-mail]
mode by
setting
REFRESH BIT
When receiving a valid packet, the RFWaves modem
(PHY layer) has to receive a “1” symbol each time a
certain period has elapsed in order to maintain its
sensitivity. The time between adjacent “1” symbols is
determined by the value of the reference capacitor.
This constraint is transparent to the application layer
since the RFW-D100 adds a “1” symbol (refresh bit) if
too many “0” symbols are transmitted consecutively.
On the receiver side, these additional “1” symbols
(refresh bits) are removed by the RFW-D100.
This refresh bit is transparent to the application layer.
The only thing the application layer has to do is
initialize
consecutive x “00” bytes.
The RFW-D100 has the flexibility to add a refresh bit
every 1 to 7 bytes. This is configured by RB(0:2) bits in
PPR register. The value of RB(0:2) bits in PPR register
determines the overhead the refresh bit has on the
throughput of the link.
The refresh bit does not add substantial overhead to
the bit stream, since it is only added when the number
of consecutive x “00” bytes exceeds a certain value.
The data that is sent is application dependent, so the
application can be adjusted so that there will be a
negligible probability of this event occurring.
Example of how to calculate the refresh bit value:
Typical RFWaves capacitor: C=1 nF
Normal discharge current = 200 nA
Each 10 mV on the capacitor represent 1 dB in
receiving power.
The capacitor is charged with each received “1”
symbol.
The receiver is allowed to lose about 2 dB before a
new “1” is received.
Thus, after each 100 consecutive “0” bits in 1 Mbps
(100 µsec), a “1” symbol should be sent.
In this case, setting RB(0:2) in PPR register to be 7
(“111”) would be sufficient (7 bytes = 56 bits).
When RB(0:2) bits are set to “000” a refresh bit is
added to every transmitted byte, regardless of its
content. This introduces a constant overhead of
12.5 %.
BIT STRUCTURE
The RFW-D100 uses an oscillator ranging from
6 ⇔ 24 MHz. In order to determine the output and input
bit rate, the RFW-D100 must be configured to the
Δ
t
=
C
⋅
I
Δ
the
V
=
1
maximum
nF
200
⋅
10
nA
mV
Vishay RFWaves
=
allowed
50
µs
RFW-D100
www.vishay.com
number
of
9