4

Data Sheet

AS2590

Rev. 1

Dec. 1993

Description

Operating Modes

The following two operating modes are pin selectable:

Mode 0:

Clock and timer are disabled and the oscillator is stopped

when going on-hook (command BLANK ALL).

Mode 1:

Clock and timer functions are enabled, clock is displayed

both during off- and on-hook (assuming that clock is set).

When going from off-hook to on-hook, the timer content

(elepsed time) is displayed for 6 seconds (assuming that

a start timer command was received).

Clock

After a power up reset the clock is disabled. The clock

will not be displayed until a valid set clock procedure has

been performed (mode 1 only). The format of the clock

is hh:mm and the leading zero of the hours is suppressed

and symbol 5 (:) is blinking with a frequency of 1 Hz. The

timer is running when off-hook and displayed for 6

seconds when going on-hook. The content of the timer

(elapsed time) is shown in stead of the clock in the format

mm:ss.

If a SET CLOCK command is received the display is

blanked, four underscore symbols are displayed where

the 4 digits of the clock will be entered (the 4 most right

digits) and symbol 5 is turned on (_ _ : _ _). The next 4

data words are interpreted as the time (hh mm). The

fourth digit terminates the SET CLOCK and starts the

clock with the seconds set to zero.

If less than 4 data words (digits) are received the first

command (normally a BLANK DIGITS or a BLANK ALL)

will terminate the SET CLOCK. But as the procedure

was incomplete, it is regarded as invalid and further

clock display is disabled. The next valid SET CLOCK

command will enable the clock again. The SET CLOCK

command does not effect the timer.

The time-out condition (approx. 15 seconds) when setting

clock is recognized by the dialler/controller (e.g. AS2574).

If a time-out condition occours the dialler sends a

BLANK ALL command to terminated the SET CLOCK.

Timer

The following commands effect the timer:

- START TIMER and START FIFO; they start the timer.

If the timer is already running, it cannot be restarted

by one of these commands before stopping the timer

with the BLANK ALL command.

- Power up; enables subsequent start timer commands.

- BLANK ALL; clears the whole display (including special

symbols) and displays the timer contents for 6 seconds

(if clock/timer function is enabled) or until a new

START TIMER/FIFO command is received. Then it

returns to normal display mode.

- if any command or data is received by the serial

interface within the time out period after a BLANK ALL

command, the timer display will be blanked or replaced

by the clock display.

The timer is displayed in the format mm:ss with the

leading zero of the minutes suppressed and symbol 5 (:)

turned on.

LCD Outputs

The 33 segment outputs and 4 backplane outputs can

drive a customized liquid crystal display in 1:4 multiplex

mode. Two reference voltages V1/3 and V2/3 are

provided by an external voltage divider.

Digits and Special Symbols

The display consists of 18 seven segment digits and 6

special symbols (see figure 1):

- D0…D17; D0 is the most left seven segment digit, the

possible numbers displayed by one digit are shown in

figure 2. The symbol (_) is only displayed at D13, D14,

D16 and D17 when setting the clock.

- SB0…SB5; 6 special symbols (one segment for each

symbol only), see figure 1 for reference. If SB0

(loudspeaker on) or SB1 (microphone muted) are

turned on, they blink with a frequency of 1 Hz.

Multiplex Mode

A total of 132 segments are addressable. One output

drives 4 segments in a time multiplex mode. The 4

backplane outputs determine the currently addressed

segment (see figure 3).

Figure 3 gives the correlation between segment outputs

and addressed segments.

Data and Commands

32 different words may be received via the serial interface.

19 words are interpreted as display data for one of the

18 seven segment digits. Table 2 gives the translation

from received code to displayed symbol.

13 words are valid commands codes. The function of

each command is described in table 2, and table 4 lists

the 5 bit codes for all possible commands.