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73K302L
Bell 212A, 103, 202
Single-Chip Modem
4
PIN DESCRIPTION
POWER
NAME
PLCC/PIN
DIP NUMBER
TYPE
DESCRIPTION
GND
28
I
System Ground.
VDD
15
I
Power supply input, 5V ±10%. Bypass with 0.1 and 22 μF capacitors
to GND.
VREF
26
O
An internally generated reference voltage. Bypass with 0.1 μF
capacitor to GND.
ISET
24
I
Chip current reference. Sets bias current for op-amps. The chip
current is set by connecting this pin to VDD through a 2 M
resistor.
ISET should be bypassed to GND with a 0.1 μF capacitor.
PARALLEL MICROPROCESSOR INTERFACE
ALE
12
I
Address latch enable. The falling edge of ALE latches the address on
AD0-AD2 and the chip select on
CS
.
AD0-AD7
4-11
I/O
Address/data bus. These bidirectional tri-state multi-plexed lines carry
information to and from the internal registers.
CS
20
I
Chip select. A low on this pin during the falling edge of ALE allows a
read cycle or a write cycle to occur. AD0-AD7 will not be driven and
no registers will be written if
CS
(latched) is not active. The state of
CS
is latched on the falling edge of ALE.
CLK
1
O
Output clock. This pin is selectable under processor control to be
either the crystal frequency (for use as a processor clock) or 16 times
the data rate for use as a baud rate clock in DPSK mode only. The
pin defaults to the crystal frequency on reset.
INT
17
O
Interrupt. This open drain output signal is used to inform the
processor that a detect flag has occurred. The processor must then
read the detect register to determine which detect triggered the
interrupt.
INT
will stay low until the processor reads the detect register
or does a full reset.
RD
14
I
Read. A low requests a read of the 73K302L internal registers. Data
cannot be output unless both
RD
and the latched
CS
are active or low.
RESET
25
I
Reset. An active high signal on this pin will put the chip into an inactive
state. All control register bits (CR0, CR1, Tone) will be reset. The
output of the CLK pin will be set to the crystal frequency. An internal
pull down resistor permits power on reset using a capacitor to VDD.