STV82X7 datasheet(51/156 Pages) STMICROELECTRONICS

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STV82x7

I²C Interface

11.2

Start-up and Configuration Change Procedure

The DSP running loop is:

● Read IC registers and update internal structures (memory variables)

● Process sound samples

● Write I²C registers with new updated values

The step “process sound sample” duration is 1ms. This is shown in Figure 30.

When programming I²C read/write register with addresses between 80h and FFh this flow has to be

taken into account.

For example, if two different values are written in the same register in less than 2 ms, it is possible

that the DSP doesn’t see the first value (because the second value over-writes the first one during

the “DSP processing” phase, before DSP can read the registers again).

In the same way, when waiting for a register value change, the software programme must wait for at

least 2 ms in order to allow sufficient time for the DSP to update the register values.

Figure 30: Simplified DSP Processing Flow

(DSP RUN)

HW_RESET bit = 1

(bit 2 in HOST_CMD register)

INIT_MEM bit status?

(bit 0 in DSP_STATUS register

(DSP Initialization)

(Start DSP Processing)

HOST_RUN bit = 1

(bit 0 in DSP_RUN register)

(Simultaneously read the

128 I²C registers)

(DSP processing time = 1ms)

(Simultaneously write the

Load Patch File

Read I²C Registers

Update internal Structures

DSP Processing

Update I²C Registers

I²C Registers

(HW space)

80h

81h

82h

83h

84h

...

FEh

FFh

128 I²C registers)

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