|
|
Part: FX469J
Category:
Communication
-> Modems
-> Low-speed Modems
Description: 1200/2400/4800 Baud FFSK Modem
Company: Consumer Microcircuits Limited
Datasheet: Download FX469J datasheet File size : 227 kB
Request For quote: Find where to buy FX469J
Datasheet text preview:
CML Semiconductor Products
PRODUCT INFORMATION
FX469
Features Selectable Data Rates 1200, 2400 and 4800 Baud Full-Duplex FFSK Rx and Tx Bandpass Filters Clock Recovery and Carrier Detect Facilities Rx and Tx Enable Functions
Tx GENERATOR Tx DATA I/P Tx ENABLE CLOCK RATE Tx FILTER
1200/2400/4800 Baud FFSK Modem
Publication D/469/6 April 1998
Pin Selected Xtal/Clock Inputs 1.008MHz or 4.032MHz Radio and General Applications Data-Over-Radio PMR and Cellular Signalling Portable Data Terminals Personal/Cordless Telephone
Tx SIGNAL O/P Tx SYNC O/P
VDD
XTAL/CLOCK CLOCK OSCILLATOR XTAL 1200/2400 BAUD SELECT 4800 BAUD SELECT BANDPASS O/P Rx ENABLE Rx SIGNAL I/P Rx FILTER LIMITER RETRIGGERABLE MONOSTABLE DIGITAL FILTER DATA FILTER LIMITER UNCLOCKED DATA O/P DIVIDER
f ..
V BIAS
n
VSS
FX469
RECTIFIER DIGITAL PLL DATA LATCH
CLOCKED DATA O/P Rx SYNC O/P
NOISE FILTER
RECTIFIER S/N COMPARATOR CARRIER DETECT TIME CONSTANT CARRIER DETECT O/P
Fig.1 Functional Block Diagram
Brief Description
The FX469 is a single-chip CMOS LSI circuit which operates as a full-duplex pin-selectable 1200, 2400 or 4800 baud FFSK Modem. The mark and space frequencies are 1200/1800, 1200/2400 and 2400/4800 Hz respectively. Tone frequencies are phase continuous; transitions occur at the zero crossing point. Employing a common Xtal oscillator with a choice of two clock frequencies (1.008MHz or 4.032MHz) to provide baud-rate, transmit frequencies, and Rx and Tx synchronization, the transmitter and receiver operate entirely independently including individual section powersave functions. The FX469 includes on chip circuitry for Carrier Detect and Rx Clock recovery, both of which are made available as output pins.
1
Rx, Tx and Carrier Detect paths each contain a bandpass filter to ensure the provision of optimum signal conditions both in the modem and for the Tx modulation circuitry. The FX469 demonstrates a high sensitivity and good bit-error-rate under adverse signal conditions; the carrier detect time constant is set by an external capacitor, whose value should be arranged as required to further enhance this product's performance in high noise environments. This low-power device requires few external components and is available in small outline plastic (S.O.I.C) and cerdip DIL packages.
Pin Number
FX469 DW LG/LS J/P6 1 1 1
Function
Xtal/Clock : The input to the on-chip inverter, for use with either a 1.008MHz or a 4.032MHz Xtal or external clock. Clock frequency selection is by the "Clock Rate" input pin. The selection of this frequency will affect the operational Data Rate of this device. Refer to Baud Selection information on the next page. Operation of any CML microcircuit without a Xtal or clock input may cause device damage. To minimise damage in the event of a Xtal/drive failure. it is recommended that the power rail (VDD) is fitted with a current limiting device (resistor or fast-reaction fuse).
2
2
2
XtalN : Output of the on-chip inverter.
3
3
3
Tx Sync O/P : A squarewave, produced on-chip, to synchronize the input of logic data and transmission of the FFSK signal (See Figure 4).
4
5
5
Tx Signal O/P : When the transmitter is enabled, this pin outputs the (140-step pseudo sinewave) FFSK signal (See Figure 4). With the transmitter disabled, this output is set to a high-impedance state.
5
7
6
Tx Data I/P : Serial logic data to be transmitted is input to this pin.
6
8
7
Tx EnableN : A logic `0' will enable the transmitter (See Figure 4). A logic `1' at this input will put the transmitter into powersave whilst forcing "Tx Sync Out" to a logic `1' and "Tx Signal Out" to a high-impedance state. This pin is internally pulled to VDD.
7
9
8
Bandpass O/P : The output of the Rx Bandpass Filter. This output impedance is typically 10kW and may require buffering prior to use.
8
10
9
Rx Enable : The control of the Rx function. The control of other outputs is given below. Rx Enable = Rx Function Clock Data O/P Carrier Detect Rx Sync Out "1" = Enabled Enabled Enabled Enabled "0" = Powersave "0" "0" 1" or "0"
9
11
10
VBIAS: The output of the on-chip analogue bias circuitry. Held internally at VDD/2, this pin should be decoupled to VSS by a capacitor (C2). (See Figure 2. This bias voltage is maintained under all powersave conditions.
10
12
11
VSS: Negative supply rail (GND).
2
Pin Number
DW 11 FX469 LG/LS 13 J/P6 12
Function
Unclocked Data O/P: The recovered asynchronous serial data output from the receiver.
12
14
13
Clocked Data O/P: The recovered synchronous serial data output from the receiver. Data is latched out by the recovered clock, available at the "Rx Sync O/P," (See Figure 5).
13
15
14
Carrier Detect O/P: When an FFSK signal is being received this output is a logic `1.'
14
16
15
Rx Signal I/P: The FFSK signal input for the receiver. This input should be coupled via a capacitor, C3.
15
18
17
Rx Sync O/P: A flywheel squarewave output. This clock will synchronize to incoming Rx FFSK data (See Figure 5).
16
19
16
1200/2400 Baud Select: A logic `1' on this pin selects the 1200 baud option. Tone frequencies are: one cycle of 1200Hz represents a logic `1,' one-and-a-half cycles of 1800Hz represents a logic `0.' A logic `0' on this pin selects the 2400 baud option. Tone frequencies are: one-half cycle of 1200Hz represents a logic `1,' one cycle of 2400Hz represents a logic `0.' This function is also used, in part, to select the 4800 baud option. This pin has an internal 1MW pullup resistor. Operational Data Rate Configurations are illustrated in the table below. Xtal/Clock Frequency Clock Rate pin 1200/2400 Select pin 4800 Select pin Baud Rate 1.008MHz 0 0 1 0 0 0 1200 2400 4.032MHz 1 1 0 0 0 1 2400 4800
1 1 0 1200
17
20
18
4800 Baud Select: A logic `1' on this pin combined with a logic `0' on the 1200/2400 Baud Select pin will select the 4800 option (1MW pulldown resistor). Tone frequencies are: one-half cycle of 2400Hz represents a logic `1,' one cycle of 4800Hz represents a logic `0.' This state can only be achieved using a 4.032MHz Xtal input.
18
21
19
Clock Rate: A logic input to select and allow the use of either a 1.008MHz or 4.032MHz Xtal/clock. Logic `1' = 4.032MHz, logic `0' = 1.008MHz. This input has an internal pulldown resistor (1.008MHz).
19
22
20
Carrier Detect Time Constant : Part of the carrier detect integration function. The value of C4 connected to this pin will affect the carrier detect response time and hence noise performance (See Figure 2, Note 3).
20
24
22
VDD: Positive supply rail. A single 5-volt supply is required.
4, 6, 17, 23
4, 21
No internal connection, do not use.
3
Others parts begin by fx
FX-1 FX-2 FX-3 FX-4
|
|
|
