AD1816A

–20–

REV. A

PNPR

Plug and Play Reset flag. This bit is set by an AD1816A reset (RESETB pin asserted LOW) or by a Plug and Play

reset command. This bit is cleared by the assertion of the FCLR bit in the control word. While this bit is set, all at-

tempts to write an SS indirect register via the DSP port will be ignored and fail. This is to ensure that Plug and

Play resets are immediately applied to the application running on the DSP, without requiring them to continuously poll

the Plug and Play reset status bit. During the frame in which this bit is cleared (by asserting FCLR), an attempt to

write an SS indirect register will succeed. If the FCLR bit is continuously asserted, writes to indirect registers via

the DSP port will always be enabled. A Plug and Play reset command will set this PNPR bit HIGH during at least

one frame.

PDN

Power-Down flag. This bit is set by an AD1816A reset (RESETB pin asserted LOW), or by an AD1816A power-

down. Before an AD1816A power-down sequence shuts down the DSP port, at least one frame will be sent with

this bit set. This bit can be cleared by the assertion of the FCLR (DSP port status clear) bit in the control word,

providing the AD1816A is no longer in power-down.

The SDFS pin is used for the serial interface frame synchronization. New frames are marked by a one SCLK duration HI pulse,

driven out on SDFS, one serial clock period before the frame begins. Upon initializing, there are exactly 12 time slots per frame and

16 bits per time slot. The frame rate is 57,291 and 2/3 Hz (11 MHz SCLK /(16 bits

× 12 slots)). The frame rate can also be changed

from the default value by reprogramming the rate in registers. The frame rate can run at the default rate or be programmed to match

the modem sample rate, ADC capture rate, DAC playback rate, music sample rate, I

the frame rate is not equivalent to the sample rate, Valid Out, Request In and Valid In bits are used to control the sample data flow.

When the frame rate is equivalent to the sample rate, Valid and Request bits can be ignored.

SCLK

SDI OR SDO

SDFS

15 14 13

0

1

2

3

SAMPLE PERIOD N

SLOT 0

SLOT 15

SLOT 0

SLOT 15

SLOT 0

SLOT 15

SAMPLE PERIOD N + 1

SAMPLE PERIOD N + 2

15 14 13

0

1

2

3

15 14 13

0

1

2

3

Figure 12. DSP Serial Interface (Default Frame Rate)

15 14 13

0

1

2

3

15 14 13

0

1

2

3

15 14 13

0

1

2

3

SCLK

SDI OR

SDO

SDFS

SAMPLE PERIOD N

SLOT 0

SLOT 15

SLOT 0

SLOT 15

SLOT 0

SLOT 15

SAMPLE PERIOD N + 1

SAMPLE PERIOD N + 2

Figure 13. DSP Serial Interface (User Programmed Frame Rate)