M494 datasheet(8/22 Pages) STMICROELECTRONICS

Part #	M494

Description	SINGLE-CHIP VOLTAGE TUNING SYSTEM WITH 4 ANALOG CONTROLS AND mP INTERFACE

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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FUNCTIONAL DESCRIPTION (continued)

Display

The M494 is capable of directly driving a 1 digit

common anode LED display at the max. sink cur-

rent of 15mA per segment. The h+i pin is capable

of sinking a max. current of 30mA so that these two

segments can be driven from the same pin and be

the same brightness as the other segments.

On instruction from the internal command decoder

the display shows programme number, direction of

analog control movement, decade change or Mem-

ory Addressing function active. Analog controls in

this context are defined as Tuning, Volume, Con-

trast, Saturation & Brightness. The formats of the

display for analog control direction, decade change

and Memory Addressing are shown below respec-

tively :

For the analog controls the above condition is

displayed with an ”overrun” time of 300ms. i.e. the

display will show the ”arrows” for a period of

300ms after the release of any analog control up

or down key. The Memory Addressing function

display flashes at 5Hz after the Memory Addressing

function is commanded and continues to flash until

a programme is selected or any other command is

given. In 1 * the g segment only flashes at 5Hz and

continues to flash until a programme number is

selected or any other command is given. If in

Memory Addressing and 1 * is pressed then the

display above is shown with segments g & d only

flashing at 5Hz until a programme number is se-

lected or any other commands is given. When

Store or Set Skip Flag commands are executed the

whole display is flashed at 5Hz for 1 second.

Keyboard

It is possible to implement a keyboard with a max.

size of 35 keys as a 5 x 7 array. Fig. 8 shows the

arrangement of the key matrix. Each key connects

a row (a-g) with a column (D0-D4) with a max.

resistance of 10k

Ω. De-bounce logic is integrated

on the chip that only allows acceptance of a com-

mand if the key is closed for longer than 40ms

except for the On/Standby and On/Off commands

where the relevant keys must be closed for approxi-

mately 100ms. This is equivalent to 2 received RC

commands).

UP

DOWN

MEMORY

ADDRESSING

|*

I* AND

MEM. ADDR.

For the main keyboard matrix (a-g x D0-D4), if the

logic detects two keys closed simultaneously the

display is blanked to indicate this condition to the

user and no command is executed. When the logic

detects only one key pressed the display will re-il-

luminate and the command be executed.

This avoids confusion as to which command should

be executed and provides feed back to the user.

For the Option select line all options/commands

can be active simultaneously.

1 * mode or decade mode can be selected on the

option select line by the presence of a diode or not

respectively. These two modes are only active for

the 20 program option and are described below :

In 1 * mode the display will toggle in & out of the

condition shown in the Display Section. Access to

programs in the first decade is made by simply

pressing any 0-9 program key and access to pro-

grams in the second decade, whatever the current

program is made by pressing 1 * followed by any

0-9 program key.

In decade mode on pressing either

±10 (decade)

keys the display will light or extinguish the half digit

respectively and simultaneously effect the tuning

information. e.g. if the device is in program 3 press-

ing + 10 (decade) key will give program 13 and then

pressing - 10 (decade) key will give program 3.

Pressing - 10 (decade) again will have no effect.

The 20 program option select acts like an enable

for the 1 * or decade modes. i.e. the 1 * or decade

modes are only selectable in the 20 program op-

tion. In 16 program option the function of the 1*

key, program key 0, -10 (decade) & + 10 (decade)

are changed to no function, programme 10, 11 &

12 respectively. i.e. The difference between fig. 7

& 8 for those keys that change function.

If the 1 * key is pressed followed by brightness up

for example the device will increase the brightness

only and reset the 1 * command i.e. the last

command from any command source will al-

ways be executed if it is a single keystroke

command and the 1 * command will be reset by

it. It is possible to press the 1 * key on the keyboard

and then a program 0-9 command from RC or Data

command sources or vice versa. Thus there are 2

methods of selecting a program from the keyboard

for the 16 program option : direct access (only up

to 12 programs) or Memory sequence up/down.

And there are 3 methods of selecting a program

from the keyboard for the 20 program option : 1 *

mode, decade mode and Memory sequence

up/down.

M494

8/22

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