3.5.1
Manual Bank Selection
3.5.2
Automatic Bank Selection
3.5.2.1 Coefficient Write Operations While Automatic Bank Switch Is Enabled
3.5.3
Bank Set
3.5.4
Bank-Switch Timeline
TAS5508
8-Channel Digital Audio PWM Processor
SLES091D – FEBRUARY 2004 – REVISED JULY 2009
www.ti.com
The three bank selection bits of the bank control register allow the appropriate bank to be manually
selected (000 = bank 1, 001 = bank 2, 010 = bank 3). In the manual mode, when a write occurs to the
biquad, DRC, or loudness coefficients, the currently selected bank is updated. If audio data is streaming to
the TAS5508 during a manual bank selection, the TAS5508 first performs a mute sequence, then
performs the bank switch, and finally restores the volume using an unmute sequence.
A mute command initiated by the bank-switch mute sequence overrides an unmute command or a volume
command. While a mute is active, the commanded channels are muted. When a channel is unmuted, the
volume level goes to the last commanded volume setting that has been received for that channel.
If MCLK or SCLK is stopped, the TAS5508 performs a bank-switch operation. If the clocks start up once
the manual bank-switch command has been received, the bank-switch operation is performed during the
5-ms, silent-start sequence.
To enable automatic bank selection, a value of 3 is written into the bank selection bits of the bank control
register. Banks are associated with one or more sample rates by writing values into the bank 1 or bank 2
data-rate selection registers. The automatic bank selection is performed when a frequency change is
detected according to the following scheme:
1. The system scans bank-1 data-rate associations to see if bank 1 is assigned for that data rate.
2. If bank 1 is assigned, then the bank-1 coefficients are loaded.
3. If bank 1 is not assigned, the system scans bank 2 to see if bank 2 is assigned for that data rate.
4. If bank 2 is assigned, the bank 2 coefficients are loaded.
5. If bank 2 is not assigned, the system loads the bank 3 coefficients.
The default is that all frequencies are enabled for bank 1. This default is expressed as a value of all 1s in
the bank-1 auto-selection byte and all 0s in the bank-2 auto-selection byte.
In automatic mode, if a write occurs to the tone, EQ, DRC, or loudness coefficients, the bank that is
written to is the current bank.
Bank set is used to provide a secure way to update the bank coefficients in both the manual and
automatic switching modes without causing a bank switch to occur. Bank-set mode does not alter the
current bank register mapping. It simply enables any bank coefficients to be updated while inhibiting any
bank switches from taking place. In manual mode, this enables the coefficients to be set without switching
banks. In automatic mode, this prevents a clock error or data rate change from corrupting a bank
coefficient write.
To update the coefficients of a bank, a value of 4, 5, or 6 is written into in the bank selection-bits of the
bank control register. This enables the tone, EQ, DRC, and loudness coefficient values of bank 1, 2, or 3,
respectively, to be updated.
Once the coefficients of the bank have been updated, the bank-selection bits are then returned to the
desired manual or automatic bank-selection mode.
After a bank switch is initiated (manual or automatic), no I2C writes to the TAS5508 should occur before a
minimum of 186 ms. This value is determined by the volume ramp rates for a particular sample rate.
TAS5508 Controls and Status
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