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RESET OPERATION

1024 System Clock Periods

Required for Initialization

System Clock

Indeterminate

or Inactive

SCKI

~ 2.0V

~ 4.0V

0V

0V

0V

0V

Internal

Reset

V

V

V

DD

PCM4104-EP

SBAS419 – JUNE 2007

The PCM4104 includes three reset functions: power-on, external, and software-controlled. This section

describes each of the three reset functions.

On power up, the internal reset signal is forced low, forcing the PCM4104 into a reset state. The power-on reset

PCM4104 then waits for the system clock input (SCKI) to become active. Once the system clock has been

detected, the initialization sequence begins. The initialization sequence requires 1024 system clock periods for

completion. When the initialization sequence is completed, the PCM4104 is ready to accept audio data at the

audio serial port. Figure 5 shows the power-on reset sequence timing.

If the PCM4104 is configured for Software mode control via the SPI port, all control registers will be reset to their

default state during the initialization sequence. In both Standalone and Software modes, the analog outputs for

all four channels are muted during the reset and initialization sequence. While in mute state, the analog output

The user may force a reset initialization sequence at any time while the system clock input is active by utilizing

the RST input (pin 9). The RST input is active low, and requires a minimum low pulse width of 40 nanoseconds.

The low-to-high transition of the applied reset signal will force an initialization sequence to begin. As in the case

of the power-on reset, the initialization sequence requires 1024 system clock periods for completion. Figure 6

illustrates the reset sequence initiated when using the RST input.

A reset initialization sequence is available in Software mode, using the RST bit in Control Register 6. The RST

bit is active high. When RST is set to 1, a reset sequence is initiated in the same fashion as an external reset

applied at the RST input.

Figure 7 shows the state of the analog outputs for the PCM4104 before, during and after the reset operations.

Figure 5. Power-Up Reset Timing

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