CS4298 Datasheet, PDF (44/52 Pages) Cirrus Logic – SoundFusion Audio/Modem Codec 97 (AMC 97)

CS4298
XTL_OUT - Crystal Output
This pin is used for a crystal placed between this pin and XLT_IN. If an external clock is used
on XTL_IN or the codec is in BIT_CLK mode, this pin must be left floating with no traces or
components connected to it.
ID1#, ID0# - Codec ID, Inputs
These pins select the codec ID and mode of operation for the CS4298. They are sampled after
the rising edge of RESET# and not used after. These inputs have internal 100 kΩ pull-ups and
should be left floating for a logic 0 or tied to analog ground for a logic 1. The pins utilize
inverted logic, so the condition of both pins floating sets the codec to primary mode while any
other combination sets the codec to a secondary mode. In primary mode, the codec is always
clocked from an external crystal or an external oscillator connected to the XTL_IN and/or
XTL_OUT pins with BIT_CLK as an output. In secondary mode, the clocking mechanism is
determined by the state of the BCM# pin with BIT_CLK always being an input.
BCM# - BIT_CLK Mode, Input
This pin selects the secondary mode clocking mechanism. BCM# is sampled after the rising
edge of RESET# and not used after. In codec secondary mode (ID1# and or ID0# grounded),
grounding this input will select BIT_CLK mode. In this mode, BIT_CLK is defined as an input
and all internal timing will be derived from the BIT_CLK signal and no connections should be
made to XTAL_IN and XTAL_OUT. When BCM# is floating, all timing will be derived from
the XTAL_IN pin. In this case, XTAL_IN must be syncronous to BIT_CLK. In primary mode,
BCM# must be left floating.
S/PDIF_OUT - Sony/Phillips Digital Interface, Output
This pin generates IEC 958 consumer compatible (S/PDIF) digital output from the CS4298
using output slots 6 and 9 when the SPDIF_EN bit in register 68h is set. For use with consumer
audio equipment, the output may be used to drive an RS422A compliant interface through an
isolation transformer, or a CP-1201 compliant interface through a TOSLINK module. When
S/PDIF_OUT is not being used this output is driven to a logic ‘0’.
GPIO[9:0] - General Purpose Input/Output
These GPIO pins are used to control modem DAAs and other discrete digital functions. When a
GPIO pin is configured as an input, it behaves as a Schmitt trigger input with 350 mV of
hysteresis at 5 V and 220 mV of hysteresis at 3.3 V. When a GPIO pin in configured as an
output, it may function as a normal CMOS output (4 mA drive) or as an open drain output.
GPIO pins power up in the high impedance state (tri-state).
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