FX809LG 查看數據表（PDF） - CML Microsystems Plc

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FX809LG

FFSK Modem

CML Microsystems Plc 

Pin Number Function

FX809

J/LG/LS

1

Xtal: The output of the on-chip clock oscillator. External components are required at this input

when a Xtal input is used. See Figure 2, INSET.

2

Xtal/Clock: The input to the on-chip clock oscillator inverter. A Xtal or externally derived clock

should be connected here. See Figure 2, INSET.

3

Interrupt Request (IRQ): The output of this pin indicates an interrupt condition to the

µController, by going to a logic “0.” This is a “wire-or able” output, enabling the connection of

up to 8 peripherals to 1 interrupt port on the µController. This pin has a low-impedance

pulldown to logic “0” when active and a high-impedance when inactive. The system IRQ line

requires a 'pull-up' resistor to VDD.

The conditions that cause interrupts are indicated in the Status Register and are shown below:

Tx Idle

Rx Data Ready

Tx Data Ready

Rx SYNC Detect

Rx SYNC Detect

Interrupt outputs can be disabled by bit 3 of the Control Register.

No Internal connection.

4

No Internal connection.

5

Rx Freeformat: Used in the Rx mode, this input, when a logic “0,” allows received data to be

6

read from the Rx Data Buffer via the Reply Data line without having to acheive byte

synchronization (SYNC/SYNC) first. Data will continue to be available after this input goes to a

logic “1” until either a SYNC or SYNC Prime bit is set or the the modem set to Tx mode.

When held at a logic “1” the modem operates normally. This pin has an internal 1MΩ pullup

resistor.

NOTE: If this input is held at a logic “0” in the Tx mode, the Rx Data Ready bit in the Status

Register may occasionally be set, but not cause an interrupt. If this input is a logic “0” when

going into the Rx mode, an Rx Data Ready interrupt may be generated immediately, in this

case the first byte of Rx data should be ignored.

VBIAS : The internal circuitry bias line, held at VDD/2 this pin must be decoupled to VSS by

7

capacitor C , see Figure 2.

3

Amp In: The inverting input to the on-chip uncommitted amplifier .

8

Amp Out: The output of the on-chip uncommitted amplifier.

9

Rx In: The 1200 baud, 1200Hz/1800Hz, received FFSK signal input. The input signal to this

10

pin must be a.c. coupled via capacitor C , see Figure 2.

4

No Internal connection.

11

VSS: Negative Supply (GND).

12

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