Data Sheet

4-Level FSK Modem Data Pump Page 7 of 47 MX919B PRELIMINARY INFORMATION
©2001 MX•COM, INC. www.mxcom.com Tele: 800 638 5577 336 744 5050 Fax: [phone] Doc. # 20480170.003
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2. Signal List
Pin No. Signal Type Description
1
IRQ
output
A 'wire-ORable' output for connection to the host µC's Interrupt
Request input. When active, this output has a low impedance pull
down to V
SS
. It has high impedance when inactive.
2 D7 BUS
3 D6 BUS
4 D5 BUS
5 D4 BUS
6 D3 BUS
7 D2 BUS
8 D1 BUS
9 D0 BUS
Pins 2-9 (D7-D0) are 8-bit, bi-directional,
3-state µC interface data lines
10
RD
input
Read. An active low logic level input used to control the reading of data
from the modem into the host µC.
11
WR
Input
Write. An active low logic level input used to control the writing of data
into the modem from the host µC.
12 V
SS
power Negative supply (ground).
13
CS
input
Chip Select. An active low logic level input to the modem used to
enable a data read or write operation.
14 A0 input Logic level modem register select input
15 A1 input Logic level modem register select input
16
XTAL
output Output of the on-chip oscillator.
17 XTAL/CLOCK input Input to the on-chip oscillator, for an external Xtal circuit or clock.
18 DOC2 output
Connection to the Rx level measurement circuitry. Should be
capacitive coupled to V
SS
.
19 DOC1 output
Connection to the Rx level measurement circuitry. Should be
capacitive coupled to V
SS
20 TXOUT output Tx signal output from the modem.
21 V
BIAS
output
A bias line for the internal circuitry held at V
DD
/2. This pin must be
bypassed to V
SS
by a capacitor mounted close to the device pins.
22 RXIN input Input to the Rx input amplifier.
23 RXAMPOUT output Output of the Rx input amplifier.
24 V
DD
power
Positive supply. Levels and voltages are dependent upon this supply.
This pin should be bypassed to V
SS
by a capacitor mounted close to
the device pins.
Table 1: Signal List