Datasheet

Header

#Waveforms x 5 bytes

Waveform Data

(Header Size – 1) 1 byte

RAM

2048 bytes

DRV2667

SLOS751A –MARCH 2013–REVISED JANUARY 2014

www.ti.com

HEADER FORMAT

The DRV2667 memory format includes a header that describes the location of the waveform data contents. The

first byte in the RAM at memory location 0x00 on Page 1 should be the Header Size. The Header Size points to

the last byte in the header, so the actual value stored is (Header Size – 1).

Figure 28. Data Map

The following bytes in the header function as the waveform identifiers for each waveform stored in memory. Each

waveform identifier consists of 5 bytes:

1. Start Address, Upper Byte

2. Start Address, Lower Byte

3. Stop Address, Upper Byte

4. Stop Address, Lower Byte

5. Repeat Count

Since it requires more than 8-bits to address the 2 kB memory, each start and stop address consists of two

bytes. The start address contains the location of first byte in the waveform, and the stop address contains the

location of the last byte in the waveform. The upper bytes refer to the page address, and the lower byte refers to

the specified address within page. Please take note that the upper byte interprets a "zero" as Page 1, and a 7 as

Page 8 since the waveform processing engine cannot access the control space in Page 0. Page 1 is where the

RAM boundary begins as shown in Figure 27.

The Repeat Count byte contains the number of times this waveform identifier is to be repeated when it is called

during playback. Note that for Mode 3, the waveform identifier range may cover multiple waveform chunks. The

Repeat Count in the waveform identifier will cause the entire set of mode 3 waveform chunks to be repeated the

number of times specified by the Repeat Count. For mode 2, the Repeat Count is simply the number of times

that the Nyquist-rate, waveform identifier range of data in memory is repeated. When the Repeat count value is

zero, the waveform is played indefinitely until the GO bit is cleared by the user. This is useful as an infinite repeat

function for test purposes or for long alerts that play until the user intervenes.

MODE 2 VERSUS MODE 3 SELECTION

Mode 2 (Direct Playback from RAM) requires no special signaling. The header contents described in “Header

Format” simply refer to a range of Nyquist-rate, 2’s complement data within the RAM where 0xFF is interpreted

as full-scale, 0x00 is no signal, and 0x80 is negative full-scale. The waveform is played at an 8 kHz data rate.

Mode 3 (Waveform Synthesizer Mode) is indicated by the first byte in the waveform identifier (Start Address,

Upper Byte). Since there are only 8 pages, only three bits are ever used in the “Upper Bytes.” The MSB of this

byte (bit 7) is used to signal the DRV2667 that the waveform contained by the waveform identifier is to be

interpreted as a Mode 3 waveform.

Signaling Mode 2 versus Mode 3 in this way allows the user to store both mode 2 and mode 3 waveforms, and

then recall them using the waveform sequencer without further intervention. The device logic determines the

mode of the waveform within the sequence on-the-fly during playback, so mode 2 and mode 3 waveforms may

be cascaded together by the waveform sequencer.

Product Folder Links: DRV2667