cs4237b Cirrus Logic, Inc., cs4237b Datasheet - Page 89

• Manufacturer Part Number: cs4237b
• Description: Crystalclear Advanced Audio System With 3d Sound
• Manufacturer: Cirrus Logic, Inc.

range that is four bytes. If the address range is
specified to be eight bytes, then XA2 becomes
an output for SA2 from the ISA bus.
Pin XCTL1/SINT/ACDCS/DOWN is initially
controlled by the VCEN bit in the Hardware
Configuration data. If VCEN is zero, this pin be-
comes an output for XCTL1 when the state of
the XIOW pin is sampled high during a high to
low transition of the RESDRV pin. This pin also
becomes an output for ACDCS if ACDbase is
programmed to a non-zero value. If XIOW is
sampled low and ACDbase is never programmed
to a non-zero value, SINT becomes an input for
the external Synthesizer interrupt. XIOW has an
internal pullup resistor. ACDCS takes prece-
dence over the other two functions. The first
time ACDbase is programmed to a non-zero
value, the pin converts to ACDCS. The only way
to convert back to XTAL1 or SINT is to reset
the part. VCEN has the highest precedence and
will cause this pin to convert to the DOWN
function whenever VCEN is set.
Reset and Power Down
A RESDRV pin places the part into maximum
power conservation mode. When RESDRV goes
high, the PnP registers are reset - all logical de-
vices are disabled, all analog outputs are muted,
and the voltage reference then slowly decays to
ground. When RESDRV is brought low, an in-
itialization procedure begins which causes a full
calibration cycle to occur. When initialization is
completed, the registers will contain their reset
value and the part will be isolated from the bus.
RESDRV is required whenever the part is pow-
ered up. The initialization time varies based on
whether an E
size of the data in the E
goes low, the CS4236 should not be written to
for approximately one and one half second to
guarantee that the part is ready to respond to
commands. The exact timing is specified in the
Timing Section in the front of this data sheet.
DS213PP4
2
PROM is present or not and the
2
PROM. After RESDRV
Software low-power states are available through
bits in the Control logical device register space.
This part supports the same power down bits
contained in the CS4232; however, new power
down modes are provided in CTRLbase+2 that
allow for a more efficient power management
routine. This register allows individual blocks
within the part to be powered down. See the
CONTROL INTERFACE section for more infor-
mation.
Multiplexed Pin Configuration
On the high to low transition of the RESDRV
pin, the part samples the state of the XIOR and
XIOW pins. Both of these pins have internal
100k
pulled low externally, they must be buffered be-
fore connecting to a TTL input (as in a CDROM
port) since TTL cannot be pulled low.
The state of XIOR at the time RESDRV is
brought low determines the function of the
CDROM interface pins. If XIOR is sampled
high, then CDCS, CDACK, CDINT, CDRQ are
used to input SA12, SA13, SA14, SA15 respec-
tively. If XIOR is sampled low (external
pulldown) then CDCS, CDACK, CDINT, CDRQ
become the standard CDROM interface pins.
Since many CDROM drives do not use DMA,
the CDRQ and CDACK pins are further multi-
plexed with MCS and MINT respectively. MCS
is the Modem chip select that responds to COM-
base addresses, and MINT is the modem
interrupt input. These two pins comprise logical
device 5. The first time COMbase is pro-
grammed to non-zero (assuming XIOR was
sampled low), CDACK/MCS and CDRQ/MINT
switch to MCS and MINT respectively. Once
this switch occurs, the only way to revert to the
CDROM DMA pins is to reset the part or re-
move power.
The XCTL1/SINT/ACDCS/DOWN pin state is
first determined by VCEN. If VCEN is set this
pin is forced to the DOWN volume control pin.
pullups to +5V. If either of these pins is
CS4237B
89