Specifications

26 SAM0025A-062397 ESS Technology, Inc.
ES1879 DATA SHEET
PERIPHERAL INTERFACING
PRELIMINARY
The amount of effect can be controlled by either directly
programming mixer register 52h or by allowing the
ES1879 to control the effect level automatically, based on
the stereo content of the input signal. This latter feature is
called auto-limiting. In auto-limiting, the ES1879
constantly adjusts the amount of effect based on the
stereo content of the input signal. The host software can
set a maximum effect level by programming register 52h.
This gives the auto-limiting logic an upper bound.
Master Volume
The master volume is controlled through Programmed I/O
or volume control switch inputs. The master volume
supports 6 bits per channel plus mute. When docked, the
ES1879 transmits the master volume information to the
ES978 where it takes effect after the output of the ES978
mixer.
For support of legacy master volume control, any write to
legacy mixer register 22h or 32h is translated
automatically into writes to the master volume registers.
Since mixer register 22h only has 3-bit resolution and
mixer register 32h only 4-bit resolution, a translation circuit
is included in the ES1879 that translates 3- or 4-bit volume
values into the 6-bit volume plus mute that is used by the
master volume registers. Reading a legacy master volume
register (22h or 32h) also uses a translation circuit to
convert 6-bit master volumes plus mute into 3- or 4-bit
legacy master volume numbers. Support of legacy mixer
registers can be defeated under software control.
See also “Programming the ES1879 Mixer” on page 59.
Hardware Volume Controls
VOLUP, VOLDN, and MUTE are three input pins with
internal pull-up devices. The state of these pins is AND’d
with the state of the corresponding pins of the ES978
when docked.
The VOLUP and VOLDN buttons produce a single-step
change in volume when they are first pressed, and then, if
held down, enter a fast-scrolling mode up or down. The
single-step change can be either 1 volume unit (0.75 dB)
or 3 volume units (2.25 dB) as determined by bit 5 of mixer
register 64h. In fast-scrolling mode, the step change is
always 1 volume unit.
The three inputs have debounce circuitry within the
ES1879. Each input should be held low for 40 msec or
more to be recognized as a valid button press. Each input
should be held high for 40 msec or more between button
presses. A software option allows the debounce time to be
reduced from 40 msecs to 10
µ
sec (bits 3:2 of mixer
register 64h).
A software selectable option enables the mute input to be
omitted (bits 3:2 of mixer register 64h). The mute input is
defined as the state when both up and down inputs are
low. By default, this feature is disabled.
The hardware volume inputs of the ES1879 can be used
as general-purpose inputs (see bits 5:4 of Vendor-Defined
Card-Level register 25h). In this case, they cannot be used
as volume control inputs.