M494B1 datasheet(15/22 Pages) STMICROELECTRONICS

15 / 22 page

FUNCTIONAL DESCRIPTION (continued)

Mute

The sound mute function is available as a toggle

command from all command sources.

There are other commands and functions during

which the sound is muted :

- FB/sync. coincidence - If there is no FB/sync.

coincidence under any conditions the sound is

muted.

- Start up reset - the sound is muted for approx. 1.7

seconds.

- Program change - the sound is muted for 0.6

seconds on any program change ; direct, 1 * +

0-9 program (only after the second keystroke),

±10 (decade) & Memory sequenceup/down con-

tinuous or single keystrokes.

- Standby & Off states - the sound is muted.

- Band sequence - same as program change.

The sound is demuted under the following condi-

tions :

- When the mute command is received from any

source.

- When the device is commanded On from standby

of Off, i.e. if the device was muted when the

standby command was issued then when On is

commanded it will always start up with the sound

demuted after the reset and settling period of

approx. 17 seconds.

- Volume up - if volume up is commanded whilst

the sound is muted then the volume will increase

from zero.

- Volume down - if volume down is commanded

whilst the sound is muted then there is no effect.

- Any program change - the sound is NOT de-

muted.

Momentary On Switch

Provision is made for a momentary switch con-

nected between the h+i pin and ground to force the

M494 to make Power on and Start up resets auto-

matically so that the device attains the On state

immediately.

The condition of the h+i pin is latched after the reset

period of 110ms. Therefore the period of switch

contact closure should be a min. of 120ms.

Figures. 11 & 12 respectively show in flow diagram

form the two methods for storing a station : pretun-

ing program selection and post tuning program

selection. Figures. 13, 14 & 15 show the select

programme subroutine for Figures. 11 & 12 for

either 16 program option or 20 program option with

1* or

±10 (decade modes).

M494

15/22

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