Cirrus Logic CS5460A - Manual (Page 43)

CS5460A
DS487F5 43
slow rise times and/or noisy control signals. (It is
not uncommon to experience temporary periods of
abnormally high noise and/or slow, gradual resto-
ration of power, during/after a power “black-out” or
power “brown-out” event.) Once the RESET pin is
de-asserted, the internal reset circuitry remains ac-
tive for 5 MCLK cycles to insure resetting the syn-
chronous circuitry in the device. The modulators
are held in reset for 12 MCLK cycles after RESET
is de-asserted. After a hardware or software reset,
the internal registers (some of which may drive out-
put pins) will be reset to their default values on the
first MCLK received after detecting a reset event
(see Table 3). The CS5460A will then assume its
active state. (The term active state, as well as the
other possible power states of the CS5460A, are
described in Section 4.6).
The reader should refer to Section 5 for a complete
description of the registers listed in Table 3.
4.5 Serial Port Initialization
It is possible for the serial interface to become un-
synchronized with respect to the SCLK input. If
this occurs, any attempt to clock valid CS5460A
commands into the serial interface will result in ei-
ther no operation or unexpected operation be-
cause the CS5460A will not interpret the input
command bits correctly. The CS5460A’s serial port
must then be re-initialized. To initialize the serial
port, any of the following actions can be performed:
1) Power on the CS5460A. (Or if the device is al-
ready powered on, recycle the power.)
2) Hardware Reset.
3) Issue the Serial Port Initialization Sequence,
which is performed by clocking 3 (or more)
SYNC1 command bytes (0xFF) followed by
one SYNC0 command byte (0xFE) to the serial
interface.
4.6 CS5460A Power States
Active state denotes the operation of CS5460A
when the device is fully powered on (i.e., not in
sleep state or stand-by state). Performing any of
the following actions will insure that the CS5460A
is operating in the active state:
1) Power on the CS5460A. (Or if the device is al-
ready powered on, recycle the power.)
2) Hardware Reset
3) Software Reset
In addition to the three actions listed above, if the
device is operating in sleep state or stand-by state,
waking up the device out of sleep state or stand-by
state (by issuing the Power-Up/Halt command) will
also insure that the device is set into active state.
But in order to send the Power-Up/Halt command
to the device, the serial port has to be initialized.
Therefore, successful wake-up of the device can
be insured by writing the serial port initialization se-
quence to the serial interface, prior to writing the
Power-Up/Halt command.
For a description of the sleep power state and the
stand-by power state, see the Power Down Com-
mand, located in Section 4.1.
Configuration Register: 0x000001
DC offset registers: 0x000000
Gain registers 0x400000
Pulse-Rate Register: 0x0FA000
Cycle-Counter Register: 0x000FA0
Timebase Register: 0x800000
Status Register: (see Section 5)
Mask Register: 0x000000
Control Register: 0x000000
AC offset registers: 0x000000
Power Offset Register: 0x000000
All data registers: 0x000000
All unsigned data registers 0x000000
Table 3. Default Register Values upon Reset Event