SA541 Sames, SA541 Datasheet - Page 8

• Manufacturer Part Number: SA541
• Description: PULSE/DTMF SWITCHABLE DIALLERS
• Manufacturer: Sames

4.
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SA541
Simultaneous Key Depressions: If two keys are pressed simultaneously (i.e. a
second key is pressed before the first has been verified), neither key will be accepted
until both keys are released and the correct key is pressed again.
Table 2 indicates the keypad layout for the SA54X1 family.
Dialling Mode Selection
The dialling mode may be selected via the SELECT pin (pin 2) as detailed in Table
3. Four Loop-Disconnect options are available with different Interdigit pauses (IDP)
and Break:Make ratios. If the DTMF mode is selected, dialling will remain fixed in
the DTMF mode. However, if one of the LD modes is selected, the chip will be in
LD mode in the initial off-hook condition, but may be switched to DTMF by pressing
either the or # keys, provided that dialling is not in progress. If the or # keys are
pressed during LD dialling, they will be ignored.
Once in DTMF mode, depression of either the
tone-pair to be output. Only digits entered prior to a DTMF switchover will be stored
and available for redialling (see Last Number Redial operation).
Once switched to DTMF, dialling will remain in this mode until either a Recall (Flash)
operation or until the device returns to the on-hook state.
R1
R2
R3
R4
LNR:
TBR:
Select (Pin 2)
Connected to:
V
C1
C2
C3
V
SS
DD
C1
1
4
7
Timed Break Recall (Flash)
Last Number Redial
sames
C2
2
5
8
0
Table 2: Keypad Layout
Table3: Dialling Mode Selection
Dialling
DTMF
Mode
LD
LD
LD
LD
C3
3
6
9
#
C4
TBR
LNR
IDP(ms)
800
500
500
800
or # keys will cause the relevant
B:M Ratio
2:1
2:1
3:2
3:2