CML Semiconductor Products
CDPD Wireless Modem Data Pump
FX949
Obsolete Product
1.0
1.1
Features
'For Information Only'
•
MES Full Duplex Operation
•
19.2kb/s GMSK Modulation
•
Forward Channel Decoding
•
Sleep Timer Included
•
Reverse Channel Encoding
•
3.3V and 5V Applications
•
Error Detection and Syndrome Output
•
PCMCIA Package Option
Brief Description
The FX949 is a low power CMOS integrated circuit which performs all of the real-time signal and data
format-management functions required for full-duplex operation of a CDPD Mobile End Station.
The FX949 interfaces directly with the analogue modulation and demodulation circuits of the radio and
the host radio/application processor bus.
It accepts application data from the processor, constructs a correct Reverse Channel packet containing
this data and converts the packet to GMSK analogue signals for transmission. In receive, Forward
Channel GMSK signals from the discriminator are demodulated, the packet disassembled, error
checked, and the recovered application data passed to the processor.
The FX949 is the cost, size, and power efficient alternative to DSP design solutions in high
performance OEM products for the Cellular Digital Packet Data wireless services.
1996 Consumer Microcircuits Limited
CDPD Wireless Modem Data Pump
FX949
CONTENTS
Section
Page
1.0 Features.......................................................................................................... 1
1.1 Brief Description............................................................................................ 1
1.2 Block Diagram................................................................................................ 3
1.3 Signal List....................................................................................................... 4
1.4 External Components.................................................................................... 6
1.5 General Description....................................................................................... 9
1.5.1 Software Description ....................................................................... 9
1.6 Application Notes ........................................................................................ 14
1.6.1 General.......................................................................................... 14
1.6.2 Transmitter (reverse channel) ....................................................... 14
1.6.3 Receiver (forward channel) ........................................................... 15
1.6.4 Timer ............................................................................................. 16
1.7 Performance Specification ......................................................................... 18
1.7.1 Electrical Performance .................................................................. 18
1.7.2 Packaging...................................................................................... 23
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1.2
FX949
Block Diagram
Figure 1 Block Diagram
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1.3
FX949
Signal List
Package
L4
Package
L6
Pin No.
Pin No.
2
3
4
5
7
8
9
10
8
9
10
11
12
13
14
15
D0
D1
D2
D3
D4
D5
D6
D7
BI
BI
BI
BI
BI
BI
BI
BI
12
17
VDD
Power
The positive supply rail. Levels and voltages are
dependent upon this supply. This pin should be
decoupled to VSS by a capacitor.
13
18
VBIAS
O/P
A bias line for the internal circuitry, held at
½ VDD. This pin must be decoupled by a
capacitor mounted close to the device pins (see
Figures 2 and 3).
14
19
RX SIGNAL
FEEDBACK
O/P
The output of the Rx input amplifier and the input
to the Rx filter.
15
20
RX SIGNAL
I/P
The inverting input to the Rx input amplifier.
16
17
21
22
DOC 1
DOC 2
O/P
O/P
)
)
)
18
23
TX SIGNAL
O/P
The inverted Tx signal output from the modem.
20
24
Vss
26
31
XTALN
O/P
The inverted output of the on-chip oscillator.
27
32
CLOCK/XTAL
I/P
The input to the on-chip oscillator, for external
Xtal circuit or clock.
32
36
IRQN
O/P
A 'wire-ORable' output for connection to the
controlling µP's Interrupt Request input. This
output has a low impedance pull down to VSS
when active and is high impedance when
inactive.
Signal
Name
1996 Consumer Microcircuits Limited
Description
Type
)
)
)
)
)
)
)
)
Power
8-bit bidirectional tristate µP interface
data lines.
Connections to the Rx level measurement
circuitry. A capacitor should be connected
from each pin to VSS.
The negative supply rail (ground).
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CDPD Wireless Modem Data Pump
FX949
Package
L4
Package
L6
Pin No.
Pin No.
33
37
CSN
I/P
34
38
WRN
I/P
35
39
RDN
I/P
Read. An active low logic level input used to
control the reading of data from the modem into
the controlling µP.
38
39
43
44
45
46
47
41
42
1
2
3
4
5
A6
A5
A4
A3
A2
A1
A0
I/P
I/P
I/P
I/P
I/P
I/P
I/P
)
)
)
)
)
)
)
1, 6,
11, 19,
24, 30,
36, 37,
40, 41,
42, 48
6, 7,
16, 28,
30, 40,
43, 44
)
)
)
)
)
)
21, 22,
23, 25,
28, 29,
31
25, 26,
27, 29,
33, 34,
35
)
)
)
)
Notes:
I/P =
O/P =
BI =
Signal
Name
Description
Type
Chip Select. An active low logic level input to the
modem, used to enable a data read or write
operation.
Write. An active low logic level input used to
control the writing of data into the modem from
the controlling µP.
7 logic level modem register address select
inputs.
No internal connection: leave open circuit.
Internally connected: leave open circuit.
Input
Output
Bidirectional
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1.4
FX949
External Components
Figure 2 Recommended External Components (L4)
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FX949
Figure 3 Recommended External Components (L6)
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FX949
Figure 4 Internal Block Diagram
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1.5
FX949
General Description
This device performs most of the Medium Access Control (MAC) layer functions of the CDPD
specification as well as generation of the baseband signals in the physical layer, all of which are
specifically for the Mobile End Station (M-ES). For details of the system requirements and telegram
formats, the user is referred to "Cellular Digital Packet Data System Specification", Volumes 1 to 5,
currently available from:
CDPD Forum Inc.
PO Box 809320
Chicago, IL 60686
United States of America
1.5.1
Software Description
From the programmer's viewpoint, the FX949 interface consists of a number of registers, addressable
from a 7-bit bus with data supplied on a standard 8-bit µP bus, as shown in Figure 4.
Read Only Registers
A0 - A6
HEX
ADDRES
S
RDN
WRN
CSN
REGISTER
NAME
BIT 7
(D7)
BIT 6
(D6)
BIT 5
(D5)
BIT 4
(D4)
BIT 3
(D3)
BIT 2
(D2)
$00
0
1
0
RX DATA 0
0
0
<-------------------- DATA SYMBOL 0 ------------------>
$01
0
1
0
RX DATA 1
0
0
<-------------------- DATA SYMBOL 1 ------------------>
$02
0
1
0
RX DATA 2
0
0
<-------------------- DATA SYMBOL 2 ------------------>
|
|
|
|
|
|
|
|
|
|
|
|
BIT 1
(D1)
BIT 0
(D0)
$3C
0
1
0
RX DATA 60
0
0
<------------------ DATA SYMBOL 60 ------------------->
$3D
0
1
0
RX DATA 61
0
0
<------------------ DATA SYMBOL 61 ------------------->
$3E
0
1
0
RX DATA 62
0
0
<------------------ DATA SYMBOL 62 ------------------->
$3F
0
1
0
RX SYN 1
0
0
<-- SYNDROME SYMBOL 1
>
= [ r (x) / (x + α1) ] ---
$40
0
1
0
RX SYN 2
0
0
<-- SYNDROME SYMBOL 2
>
= [ r (x) / (x + α2) ] ---
$41
0
1
0
RX SYN 3
0
0
<-- SYNDROME SYMBOL 3
>
= [ r (x) / (x + α3) ] ---
$42
0
1
0
RX SYN 4
0
0
<-- SYNDROME SYMBOL 4
>
= [ r (x) / (x + α4) ] ---
$43
0
1
0
RX SYN 5
0
0
<-- SYNDROME SYMBOL 5
>
= [ r (x) / (x + α5) ] ---
$44
0
1
0
RX SYN 6
0
0
<-- SYNDROME SYMBOL 6
>
= [ r (x) / (x + α6) ] ---
$45
0
1
0
RX SYN 7
0
0
<-- SYNDROME SYMBOL 7
>
= [ r (x) / (x + α7) ] ---
$46
0
1
0
RX SYN 8
0
0
<-- SYNDROME SYMBOL 8
>
= [ r (x) / (x + α8) ] ---
$47
0
1
0
RX SYN 9
0
0
<-- SYNDROME SYMBOL 9
>
= [ r (x) / (x + α9) ] ---
$48
0
1
0
RX SYN 10
0
0
<-- SYNDROME SYMBOL 10 = [ r (x) / (x + α10) ] ->
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FX949
$49
0
1
0
RX SYN 11
0
0
<-- SYNDROME SYMBOL 11 = [ r (x) / (x + α11) ] ->
$4A
0
1
0
RX SYN 12
0
0
<-- SYNDROME SYMBOL 12 = [ r (x) / (x + α12) ] ->
$4B
0
1
0
RX SYN 13
0
0
<-- SYNDROME SYMBOL 13 = [ r (x) / (x + α13) ] ->
$4C
0
1
0
RX SYN 14
0
0
<-- SYNDROME SYMBOL 14 = [ r (x) / (x + α14) ] ->
$4D
0
1
0
RX SYN 15
0
0
<-- SYNDROME SYMBOL 15 = [ r (x) / (x + α15) ] ->
$4E
0
1
0
RX SYN 16
0
0
<-- SYNDROME SYMBOL 16 = [ r (x) / (x + α16) ] ->
$4F
0
1
0
STATUS
SYNC
DEC
IDLE
ERROR
0
$50
0
1
0
IRQ FLAGS
SYNCF
DECF
IDLEF
TXF
TIMEF
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<---- SYNC ERRORS--->
0
0
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FX949
Read Only Register Description
RXDATA0 to RXDATA62 Registers (Hex address $00 to $3E)
These are read only registers and all 63 registers are each updated with 6-bit symbols every time a valid SYNC
occurs. This is indicated by an interrupt (see SYNC, SYNC ERRORS, and SYNC ERROR LIMIT).
SYNDROME SYMBOL 1 to 16 (Hex address $3F to $4E)
These 16, 6-bit symbols contain the syndrome calculated from the received data (RXDATA 0 to 62). The
syndrome is recalculated every time a valid SYNC occurs. An all zero pattern in the 16 syndrome symbols
indicates zero errors in the data.
STATUS Register (Hex address $4F)
This is a read only register that contains the status of the various functions on the device as described below:
SYNC
(Bit 7)
This bit is set to "1" when a forward channel synchronisation word has been
received successfully. (See SYNC ERRORS and SYNC ERROR LIMIT). This bit is
reset to "0" when the sync word has not been detected for more than 420 bits (i.e.
sync lost).
DEC
(Bit 6)
This bit indicates the decode status of the Mobile Data Base Station (MDBS) on the
forward channel. This bit is set to "1" when the station fails to decode data
successfully, and is reset to "0" when the station is successful in decoding data.
This bit will only change and be valid if SYNC (Bit 7) is set to "1".
IDLE
(Bit 5)
This bit indicates the active status of the Mobile Data Base Station (MDBS) on the
forward channel. This bit is set to "0" when the station is in an IDLE state, and reset
to "1" when the station is in a BUSY state. This bit will only change and be valid if
SYNC (Bit 7) is set to "1".
The IDLE bit is derived from a majority decision on the five consecutive busy/idle
bits, as in the CDPD specification.
The first block of data received in the forward channel will not output any data until
the sync word has been found. Once this has been found, the most recent (last) idle
bit will be output in the STATUS register, and the IDLEF bit will be set to "1" in the
IRQ FLAGS register.
The next seven idle bits are output as they come in and, so long as the sync word
remains correct, successive idle bits are output as they come in.
ERROR
(Bit 4)
This bit indicates if there are errors in RXDATA. This bit is set to "0" if all syndrome
symbols (1 - 16) are "0", i.e. no errors in the data. This bit is set to "1" if any
syndrome symbol is not "0", i.e. errors are present in the data. This bit is updated
every time a valid SYNC occurs.
SYNC ERRORS
(Bits 2, 1 and 0)
This 3-bit number indicates the number of errors received in the synchronisation
word. It is updated whenever the synchronisation word is in error less than or equal
to the number specified by the SYNC ERROR LIMIT bits of the CONTROL register.
It also implies the synchronisation word has been received successfully and sets the
SYNC bit to "1" (See SYNC above).
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FX949
IRQ FLAGS Register (Hex address $50)
This is a read only register that contains flags to indicate the source of an interrupt, as described below:
SYNCF
(Bit 7)
This bit is set to "1" when the device has decoded the sync word on the forward
channel. It also is set to "1" if, after detecting sync, it fails to detect it 420 bits later,
indicating sync has been lost. The state of sync can be read from the STATUS
register. This bit is reset to "0" after a "read" of the IRQ FLAGS register. When this
bit is set to "1" an interrupt may be generated, depending on the state of the IRQ
MASK register.
DECF
(Bit 6)
This bit is set to "1" when the decode status of the Mobile Data Base Station (MDBS)
in the forward channel changes state. The decode state can be read from the
STATUS register. This bit is reset to "0" after a "read" of the IRQ FLAGS register.
When this bit is set to "1" an interrupt may be generated depending on the state of
the IRQ MASK register.
IDLEF
(Bit 5)
This bit is set to "1" when the idle status of the Mobile Data Base Station (MDBS) in
the forward channel changes state. The idle state can be read from the STATUS
register. This bit is reset to "0" after a "read" of the IRQ FLAGS register. When this
bit is set to "1" an interrupt may be generated depending on the state of the IRQ
MASK register.
TXF
(Bit 4)
This bit is used in transmission of data from the 47 symbol "write only" buffer on the
reverse channel. This bit is set to "1" when the buffer is empty and new data can be
loaded in. It is reset to "0" after a "read" of the IRQ FLAGS register. When this bit is
set to "1" an interrupt may be generated depending on the state of the IRQ MASK
register.
TIMEF
(Bit 3)
This bit is set to "1" when the timer expires and it is reset after a "read" of the IRQ
FLAGS register. When this bit is set to "1" an interrupt may be generated depending
on the state of the IRQ MASK register.
Write Only Registers
A0 - A6
HEX
ADDRES
S
BIT 7
(D7)
BIT 6
(D6)
TX DATA 0
X
X
<------------------- DATA SYMBOL 0 ------------------->
0
TX DATA 1
X
X
<------------------- DATA SYMBOL 1 ------------------->
0
TX DATA 2
X
X
<------------------- DATA SYMBOL 2 ------------------->
RDN
WRN
CSN
$00
1
0
0
$01
1
0
$02
1
0
REGISTER
NAME
BIT 5
(D5)
BIT 4
(D4)
BIT 3
(D3)
BIT 2
(D2)
|
|
|
|
|
|
|
|
|
|
|
BIT 1
(D1)
BIT 0
(D0)
|
$2C
1
0
0
TX DATA 44
X
X
<------------------- DATA SYMBOL 44 ------------------>
$2D
1
0
0
TX DATA 45
X
X
<------------------- DATA SYMBOL 45 ------------------>
$2E
1
0
0
TX DATA 46
X
X
<------------------- DATA SYMBOL 46 ------------------>
$2F
1
0
0
TIMER
$30
1
0
0
CONTROL
ACQ
$31
1
0
0
IRQ MASK
SYNCM
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<------------------------------- 0 TO 255 SECONDS ---------------------------->
12
RXHOLD
PSRX
PSTX
CI
DEC
M
IDLEM
TXM
TIMEM
<--SYNC ERROR LIMIT--->
(SERL)
ERR
M
0
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FX949
Write Only Register Description
TXDATA0 to TXDATA46 Registers (Hex address $00 to $2E)
These 47 registers can be loaded with 6-bit symbols when the TXF bit in the IRQ FLAGS register is "1". On
loading the 47th symbol, the device will generate the 16 symbol parity code and begin the transmit sequence.
These registers are buffered, therefore after the TXF bit has gone to "1" there are 47 x 6 bit periods minus the
time to generate the 16 parity symbols in which to load all registers, i.e. approximately 14 msec. The
controlling µP has to re-load the buffer with new data within this time otherwise the old data will be sent again.
TIMER Register (Hex address $2F)
This register sets a timer to expire from 1 to 255 seconds ("0" disables and powersaves it). The time starts
from when the register is first set and expires when the programmed time has passed. On expiry, the TIMEF
bit is set in the IRQ FLAGS register and an interrupt may occur. The timer is 1-shot and does not restart until it
is programmed again. After power up the TIMEF bit should be reset to "0" in order to initialise the timer.
CONTROL Register (Hex address $30)
This register is used to control the functions of the device as described below:
ACQ
(Bit 7)
This bit controls the way in which the receiver locks onto the phase and amplitude of
the incoming signal. When a carrier has been detected, this bit should be set high
for at least 16 signal-bit periods, during which time the receiver measures the signal
level (Fast Peak Detect) and sets its phase locked loop (PLL) bandwidth wide
enough to lock to the received signal in less than 8 zero crossings. When the ACQ
bit is returned low, level measurement enters the slower but more accurate
Averaging Peak Detect mode; the PLL enters its medium bandwidth for about 30
signal-bit periods, after which time it will continue in its narrow bandwidth mode.
RXHOLD
(Bit 6)
When this bit is set to "1" the receiver "bit synchronisation" PLL will lock. It can be
used during times when the signal fades, so that when the signal returns the
receiver is still very close to good "bit synchronisation". When this bit is set to "0",
the device uses its normal PLL acquisition sequence for "bit synchronisation". When
ACQ is high, the RXHOLD bit has no effect.
PSRX
(Bit 5)
When this bit is "1" the receiver is powersaved. When this bit is "0" the receiver is
enabled. After power up, this bit should be programmed to "1" in order to initialise
the receiver.
PSTX
(Bit 4)
When this bit is "1" the transmitter is powersaved. When this bit is "0" the transmitter
is enabled. Transmission starts as soon as the PSTX bit goes to "0". Before that
time, the CI bit and the TXDATA symbols should be set up for the first transmission.
Transmission is terminated as soon as the PSTX bit goes to "1". After power up, this
bit should be programmed to "1" in order to initialise the transmitter.
CI
(Bit 3)
This bit sets the continuity indicator for transmission. It should be set to "1" when
there are more blocks to follow and set to "0" when the last block begins. The first
47 symbol block transmitted after this bit has gone from "0" to "1" is preceded by the
"dotting sequence" and the reverse synchronisation.
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SYNC ERROR
LIMIT (SERL)
(Bits 2, 1 and 0)
FX949
This 3-bit number specifies the maximum number of bits that can be in error in the
synchronisation word. When the synchronisation word is recognised with less than
or equal to this number of errors the SYNCF bit is set to "1" and the actual number of
errors is loaded into SYNC ERRORS. The RXDATA is then loaded into the registers
for "Data Symbols 0 to 62", the Rx syndrome is updated, and an interrupt may be
generated, depending on the state of the IRQ MASK register. If 5, 6 or 7 errors are
programmed to be accepted in the SYNC ERROR LIMIT, falsing of the forward
channel sync word may occur.
IRQ MASK Register (Hex address $31)
These bits prevent interrupts from occurring as detailed below:
SYNCM
(Bit 7)
When this bit is set to "1" the SYNC interrupt will be gated out to the IRQN pin. When
this bit is set to "0" the SYNC interrupt will be inhibited. This bit has no effect on the
contents of the STATUS register.
DECM
(Bit 6)
When this bit is set to "1" the DEC interrupt will be gated out to the IRQN pin. When
this bit is set to "0" the DEC interrupt will be inhibited. This bit has no effect on the
contents of the STATUS register.
IDLEM
(Bit 5)
When this bit is set to "1" the IDLE interrupt will be gated out to the IRQN pin. When
this bit is set to "0" the IDLE interrupt will be inhibited. This bit has no effect on the
contents of the STATUS register.
TXM
(Bit 4)
When this bit is set to "1" the Tx interrupt will be gated out to the IRQN pin. When
this bit is set to "0" the Tx interrupt will be inhibited. This bit has no effect on the
contents of the STATUS register.
TIMERM
(Bit 3)
When this bit is set to "1" the TIMER interrupt will be gated out to the IRQN pin.
After this bit is set to "0" the TIMER interrupt will be inhibited. This bit has no effect
on the contents of the STATUS register.
ERRM
(Bit 2)
For systems that are required to work error free and where Reed-Solomon error
correction is not implemented, this bit provides the means not to interrupt the
controlling µP if errors are detected. When this bit is set to "1" all the interrupts will
work as specified. When this bit is set to "0", the SYNC, DEC and IDLE interrupts
will be inhibited even if the on chip Reed-Solomon error detector indicates there are
errors in the data, thus not wasting the controlling µP's time with interrupts for
incorrect data.
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1.6
FX949
Application Notes
Further information on Reed-Solomon codes may be found in "Error Control Coding" by S. Lin and D.J.
Costello, published by Prentice Hall in 1983. The ISBN number is 0-13-283796-X.
The operation of the FX949 can be split into 3 sections: the Transmitter (reverse channel), the
Receiver (forward channel) and the Timer. The operational sequence of each is described below, with
reference to the internal block diagram, shown in Figure 4. Data and framing transmission structures
are shown in Figure 5 for the reverse channel and in Figure 6 for the forward channel.
1.6.1
General
(1)
After power up, enable or disable the interrupts by using the IRQ MASK register, depending on
whether the IRQN signal or direct polling of the IRQ FLAGS register is being used.
(2)
After power up, program PSRX (Bit 5 of the CONTROL register) to "1" to initialise the Rx
circuitry, i.e:
reset the interrupts
reset SYNCF, DECF, IDLEF in the IRQ FLAGS register
reset SYNC, DEC, IDLE, ERROR, SYNC ERRORS in the STATUS register
All other Rx registers are not affected and will be in a random state after power up.
(3)
After power up, program PSTX (Bit 4 of the CONTROL register) to "1" to initialise the Tx
circuitry, i.e:
set TXF in the IRQ register to "1" to indicate that the Tx buffer is empty
set the interrupt IRQN, if enabled, to request Tx data from the controlling µP
1.6.2
Transmitter (reverse channel)
(1)
After power up, a Tx interrupt is generated, if enabled, and TXF (Bit 4 of the IRQ FLAGS
register) is set, indicating the output buffer is empty.
(2)
The transmitter can now be enabled.
(3)
CI (Bit 3 of the CONTROL register) should be set to "1" when there are more Tx blocks to
follow and set to "0" for the last block. If there is only one block to be sent, i.e. the first block is
the last block, then the CI bit should be pulsed from "0" to "1" to "0" to ensure that the dotting
pattern and block sync are sent and that CI is set to "0" to indicate the presence of the last
block, except just after powersave when the dotting sequence and block sync are added
automatically.
(4)
All 47 symbols (0 to 46) are loaded into the TXDATA registers from the controlling µP, finishing
the load with the 47th symbol. This set of TXDATA registers is double buffered, therefore any
previous data can be sent again by re-loading only symbol 46, i.e. loading symbol 46 indicates
that data is ready to be sent.
(5)
The loading of symbol 46 (as above [4]) triggers the generation of a Reed-Solomon 16 symbol
parity code, based on symbols 0 to 46 in the input buffer.
(6)
The transmitter will wait for the output buffer to become empty (if it is the first transmission it
may already be empty). When this condition is met, data is transferred to the output buffer. At
this point the data and C1 bit for that block have been defined and will not change whilst setting
up for the next block to be sent.
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1.6.3
FX949
(7)
The data is EXORed with the pseudorandom sequence (PRBS) as it is transmitted. Once this
is done, the output buffer will be empty and the TXF flag with interrupt will be generated,
looping the control sequence back to the first step.
(8)
The input buffer can be re-loaded while the transmitter is transmitting.
(9)
The CI (continuity indicator) bit is automatically inserted every 9 symbols, during transmission.
(10)
The 38 bit "dotting sequence" and 22 bit block synchronisation word are added if it is the first
transmission after Tx powersave or if the CI bit has just previously gone from "0" to "1"
indicating the start of a new transmission block.
(11)
The signal generated has a data rate of 19.2k bits/sec and is filtered by a Gaussian filter with a
BT of 0.5 in the transmit section of the GMSK modem.
Receiver (forward channel)
(1)
The SYNC ERROR LIMIT (SERL) (Bits 2, 1 and 0 of the CONTROL register) is set from "0" to
"7" as required by the application.
(2)
The receiver is enabled using PSRX (Bit 5 of the CONTROL register).
(3)
The receiver is now able to receive 19.2k bits/sec data via the receive section of the GMSK
modem, comprising input filter, slicer and bit synchroniser.
(4)
A continuous stream of data is fed into the receiver input shift register.
(5)
When the controlling µP receives a carrier detect, it can pulse ACQ (Bit 7 of the CONTROL
register) in order to quickly acquire bit synchronisation. If carrier detect is not available or, due
to powersave requirements, the controlling device remains unpowered, then slower bit
synchronisation will be acquired in approximately 32 bits.
(6)
The receiver input shift register is continually monitored for the 35-bit synchronisation word
interleaved with the data. It correlates the number of errors in the synchronisation word with
the maximum number allowed (previously programmed into the SYNC ERROR LIMIT bits of
the CONTROL register). When it achieves this limit or less, valid data is assumed to be
present.
(7)
The data is EXORed with the pseudorandom sequence (PRBS) and a 16-symbol syndrome is
generated. The data and syndrome are then loaded into the Rx output registers, ready for
reading by the controlling µP.
(8)
DEC (Bit 6) and IDLE (Bit 5) of the STATUS register are set according to the data received.
(9)
SYNCF (Bit 7 of the IRQ FLAGS register) is set and an IRQ is generated. SYNC (Bit 7 of the
STATUS register) is set to "1". This indicates that a new block of data has successfully been
received and is available for reading by the controlling µP.
(10)
With the first block sync received, the device now checks the DEC and IDLE positions in the
next block of data and outputs them with interrupts as they are counted in.
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CDPD Wireless Modem Data Pump
(11)
1.6.4
FX949
On-chip circuitry predicts when the next block sync will arrive. If it arrives before that time, the
circuit is reset and the sequence loops back to step (6). If the time expires, the SYNCF and
IRQ signals will be generated and SYNC (Bit 7 of the STATUS register) will be set to "0",
indicating that block sync has been lost and DEC, IDLE and RXDATA are no longer valid.
Timer
(1)
The IRQ FLAGS register is read, to reset TIMEF (Bit 3).
(2)
The TIMER register is programmed with the time required, from 1 to 255 seconds, starting the
time-out.
(3)
IRQ and TIMEF are set when time expires.
(4)
This timer can be used to implement the "sleep mode", as described in the CDPD specification.
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CDPD Wireless Modem Data Pump
FX949
Figure 5 Reverse Channel Transmission Structure
Figure 6 Forward Channel Transmission Structure
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CDPD Wireless Modem Data Pump
1.7
Performance Specification
1.7.1
Electrical Performance
FX949
Absolute Maximum Ratings
Exceeding these maximum ratings can result in damage to the device.
Min.
-0.3
-0.3
-30
-20
-40
-40
Max.
7.0
VDD + 0.3
+30
+20
+85
+85
Units
V
V
mA
mA
°C
°C
L4 Package
Total Allowable Power Dissipation at Tamb = 25°C
... Derating
550
9
mW
mW/°C
L6 Package
Total Allowable Power Dissipation at Tamb = 25°C
... Derating
800
13
mW
mW/°C
Max.
5.5
+85
4.9155
Units
V
°C
MHz
Supply (VDD - VSS)
Voltage on any pin (wrt VSS)
Current into or out of VDD and VSS pins
Current into or out of any other pin
Storage Temperature
Operating Temperature
Operating Limits
Correct operation of the device outside these limits is not implied.
Notes
Supply (VDD - VSS)
Operating Temperature
Xtal Frequency
1996 Consumer Microcircuits Limited
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Min.
3.0
-40
4.9149
D/949/5
CDPD Wireless Modem Data Pump
FX949
Operating Characteristics
For the following conditions unless otherwise specified:
Xtal Frequency = 4.9152MHz, Bit Rate = 19.2k bits/sec,
VDD = 3.3V to 5.0V, Tamb = -40°C to +85°C.
Notes
DC Parameters
IDD (powersaved)
IDD (all enabled)
IDD (powersaved)
IDD (all enabled)
(VDD = 5.0V)
(VDD = 5.0V)
(VDD = 3.0V)
(VDD = 3.0V)
1, 10
1, 10
1, 10
1, 10
AC Parameters
Tx Output
Tx O/P Impedance (Tx enabled)
Tx O/P Impedance (powersaved)
Output Signal Level
Power up to Tx O/P Stable
2
2
7
8
Rx Input
Rx I/P Impedance (at 100Hz)
Rx I/P Amp Voltage Gain (I/P = 1mVrms at 100Hz)
Input Signal Level
Xtal/Clock Input
'High' Pulse Width
'Low' Pulse Width
Input Impedance (at 100Hz)
Gain (I/P = 1mV rms at 100Hz)
µP Interface
Input Logic "1" Level
Input Logic "0" Level
Input Leakage Current (Vin = 0 to VDD)
Input Capacitance
Output Logic "1" Level (lOH = 120µA)
Output Logic "0" Level (lOL = 360µA)
'Off' State Leakage Current (Vout = VDD)
Notes:
Min.
300
0.9
Typ.
Max.
Units
1.3
5.0
0.5
2.0
2.0
7.0
1.0
3.0
mA
mA
mA
mA
1.0
500
1.0
3
2.5
1.1
5
kΩ
kΩ
Vpk-pk
bits
1.3
MΩ
V/V
Vpk-pk
10
9
0.7
3
3
40
40
10
20
4, 5
4, 5
4, 5
4, 5
5
5, 6
6
70%
500
1.0
ns
ns
MΩ
dB
30%
+5.0
−5.0
10.0
90%
10%
10
VDD
VDD
µA
pF
VDD
VDD
µA
1.
2.
3.
4.
5.
6.
7.
Not including any current drawn from the modem pins by external circuitry.
Small signal impedance, at VDD = 5.0V and Tamb = 25°C.
Timing for an external input to the CLOCK/XTAL pin.
WRN, RDN, CSN, A0 - A6 pins.
D0 - D7 pins.
IRQN pin.
For 1111000011110000.. bit sequence, at VDD = 5.0V and Tamb = 25°C.
(output level is proportional to VDD).
8. Measured between setting PSTX to "'0" and TXSIGNAL becoming stable.
9. For optimum performance, measured at RX SIGNAL FEEDBACK pin,
for a '...11110000...' bit sequence, at VDD = 5.0V and Tamb = 25°C.
10. At Tamb = 25°C only.
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CDPD Wireless Modem Data Pump
1.7.1
FX949
Electrical Performance (continued)
Timing Diagrams
Figure 7 µP Interface Timings
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CDPD Wireless Modem Data Pump
FX949
For the following conditions unless otherwise specified:
Xtal Frequency = 4.9152MHz, VDD = 3.3V to 5.0V, Tamb = -40°C to +85°C.
Notes
Min.
Typ.
Max.
Units
µP Interface Timings (ref. Fig. 7)
tACSL
Address valid to CSN low time
0
ns
tAH
Address hold time
10
ns
tCSH
CSN hold time
0
ns
tCSHI
CSN high time
6
clock cycles
tCSRWL
CSN to WRN or RDN low time
0
ns
tDHR
Read data hold time
0
ns
tDHW
Write data hold time
0
ns
tDSW
Write data setup time
90
ns
tRHCSL
RDN high to CSN low time (write)
0
ns
tRACL
Read access time from CSN low
11
175
ns
tRARL
Read access time from RDN low
11
145
ns
tRL
RDN low time
tRX
RDN high to D0 - D7 3-state time
tWHCSL
WRN high to CSN low time (read)
tWL
WRN low time
Notes:
200
ns
50
ns
0
ns
200
ns
11. With 30pF max. to VSS on D0 - D7 pins.
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D/949/5
CDPD Wireless Modem Data Pump
1.7.1
FX949
Electrical Performance (continued)
Note:
This graph does not include the improvement in error rate that is achievable if error
correction is included in the user's application software.
Figure 8 Typical Raw Bit Error Rate
for Xtal frequency = 4.9152MHz, VDD = 5.0V, Tamb = 25°C
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CDPD Wireless Modem Data Pump
1.7.2
FX949
Packaging
Figure 9 TQFP Mechanical Outline: Order as part no. FX949L4
Figure 10 PLCC Mechanical Outline: Order as part no. FX949L6
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D/949/5
CDPD Wireless Modem Data Pump
FX949
Handling precautions: This product includes input protection, however, precautions should be taken to prevent
device damage from electro-static discharge. CML does not assume any responsibility for the use of any
circuitry described. No IPR or circuit patent licences are implied. CML reserves the right at any time without
notice to change the said circuitry and this product specification. CML has a policy of testing every product
shipped using calibrated test equipment to ensure compliance with this product specification. Specific testing
of all circuit parameters is not necessarily performed.
CONSUMER MICROCIRCUITS LIMITED
1 WHEATON ROAD
WITHAM - ESSEX CM8 3TD - ENGLAND
Telephone:
Telefax:
+44 1376 513833
+44 1376 518247