SA2531 Datasheet, PDF (6/24 Pages) Sames – VERSATILE SINGLE CHIP TELEPHONE WITH 14 NUMBER REPERTORY DIALLER

SA2531 A/B/C/E/G/U
The side tone cancellation signal is applied to the STB input.
Line Loss Compensation
When Line Loss Compensation is active the gain of the Transmit and Receive amplifiers
are changed by 6dB in accordance with the DC conditions as measured at Pins LI and
LS. When the LLC Pin is Low this adjustment in gain occurs over the range I_LINE = 20 to
50 mA. When LLC is High the range is 45 to 75mA. Note that these figures apply for R1
= R30Ω.
When the LLC Pin is open the amplifier gains remain fixed regardless of the Line Current
(see figures 6 & 7).
Dialling Functions
Valid Keys
The keypad of the SA2531 comprises a maximum of 32 keys some of which are provided
to cater for options (such as the two Recall/Flash periods). A Bi-polar scan technique is
used so that the 32 keys are scanned in a 4 x 8 matrix using only 8 pins. Two explanatory
keypad arrangements are illustrated in Figures 2 & 3.
A valid key is detected when one and only one contact closure is detected between a Row
and Column Pin. Key contacts are debounced to avoid incorrect detection.
It is also possible to drive the keypad inputs with a micro controller.
Dial Mode Selection
The default mode (LD or MF) can be selected by the Mode pin. When default LD mode
is selected, a temporary change to MF can be invoked by pressing the * key. The circuit
will revert to LD by pressing the R (or R2) key or by next on-hook.
When MF mode is selected by the mode pin, the circuit can not be changed temporary
to LD but will remain in MF.
Last Number Redial
LNR is a facility that allows resignalling of the last manually dialled number without keying
in all the digits again. The LNR is repeatable.
The current contents of the RAM are overwritten by new entries.
A manually entered number is automatically stored in the LNR RAM. The capacity of the
RAM is 31 digits. If a number greater than 31 digits is entered, the LNR facility will be
inhibited (Until new entries < 32 digits) and further entries will be buffered in a First In First
Out Memory (FIFO).
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