Single-Chip Voice Recording & Playback Device for Multiple 40- to 60-Second Messages

Page 3

Message Management

Message Management General Description

Playback and record operations are managed by on chip cir-

cuitry. There

are

several available messaging

modes

depending upon desired operation. These message modes

determine message management style, message length, and

external parts count. Therefore, the designer must select the

appropriate operating mode before beginning the design.

Operating modes do not affect voice quality; for information

on factors affecting quality refer to the Sampling Rate & Voice

Quality section.

The device supports three message management modes

(defined by the MSEL1, MSEL2 and /M8_Option pins shown

in Figures 1 and 2):

• Random access mode with 2, 4, or 8 fixed-duration mes-

sages

• Tape mode, with multiple variable-duration messages, pro-

vides two options:

- Auto rewind

-Normal

Modes cannot be mixed. Switching of modes after the device

has recorded an initial message is not recommended. If

modes are switched after an initial recording has been made

some unpredictable message fragments from the previous

mode may remain present, and be audible on playback, in

the new mode. These fragments will disappear after a record

operation in the newly selected mode. Table 1 defines the

decoding necessary to choose the desired mode.

An important feature of the APR9600 message management

capabilities is the ability to audibly prompt the user to

changes in the device’s status through the use of “beeps”

superimposed on the device’s output. This feature is enabled

by asserting a logic high level on the BE pin.

Table 1

Random Access Mode

Random access mode supports 2, 4, or 8 messages seg-

ments of fixed duration. As suggested recording or playback

can be made randomly in any of the selected messages. The

length of each message segment is the total recording length

available (as defined by the selected sampling rate) divided

by the total number of segments enabled (as decoded in

Table1). Random access mode provides easy indexing to

message segments.

Functional Description of Recording in Random Access

Mode

On power up, the device is ready to record or play back, in

any of the enabled message segments. To record, /CE must

be set low to enable the device and /RE must be set low to

enable recording. You initiate recording by applying a low

level on the message trigger pin that represents the message

segment you intend to use. The message trigger pins are

labeled /M1_Message - /M8_Option on pins 1-9 (excluding

pin 7) for message segments 1-8 respectively.

Note: Message trigger pins /M1_Message, /M2_Next,

/M7_END, and /M8_Option, have expanded names to

represent the different functionality that these pins

assume in the other modes. In random access mode

these pins should be considered purely message trig-

ger pins with the same functionality as /M3, /M4, /M5,

and /M6. For a more thorough explanation of the func-

tionality of device pins in different modes please refer

to the pin description table that appears later in this

document.

When actual recording begins the device responds with a sin-

gle beep (if the BE pin is high to enable the beep tone) at the

speaker outputs to indicate that it has started recording.

Recording continues as long as the message pin stays low.

The rising edge of the same message trigger pin during

record stops the recording operation (indicated with a single

beep).

If the message trigger pin is held low beyond the end of the

maximum allocated duration, recording stops automatically

(indicated with two beeps), regardless of the state of the mes-

sage trigger pin. The chip then enters low-power mode until

the message trigger pin returns high. After the message trig-

ger pin returns to high, the chip enters standby mode. Any

subsequent high to low transition on the same message trig-

ger pin will initiate recording from the beginning of the same

Mode

MSEL1

MSEL2

/M8_Option

Random Access 2 fixed duration messages

01

Pull this pin to VCC through 100K resistor

Random Access 4 fixed duration messages

10

Pull this pin to VCC through 100K resistor

Random Access 8 fixed duration messages

11

Becomes the /M8 message trigger input pin

Tape mode, Normal operation

00

0

Tape mode, Auto rewind operation

00

1

APR9600

APLUS