AN1500A South African Micro-Electronic Systems, AN1500A Datasheet - Page 7

• Manufacturer Part Number: AN1500A
• Description: Single Chip Telephone Demo Board
• Manufacturer: South African Micro-Electronic Systems

8 Description of keyboard functions
The user-friendly operating procedures comply with different PSTN and PABX systems worldwide. By choosing
between the total of 19 keys it is possible to fit the SA2532K into most telephone designs.
The keyboard is connected to 8 pins of the SA2532K (C1...C4, R1...R4) by a n*m SPST keyboard matrix. To
extend two of the rows, a diode (D9 and D10) are added. This arrangement allows detection of 19 keys on a 4*4
matrix.
8.1 Numeric keys
The numeric keys (1..0,!,#) are standard number dial keys for both DTMF and pulse dialing (!and # only DTMF).
Additionally the !key can be used for temporary MF switching.
8.2 Flash keys (R,R2)
Selection of flash timing can be made by selecting one of the 2 flash keys :R1= 100ms and R2= 270ms.
8.3 Last number redial key (LNR)
The last number redial facility allows redialing of the last manually entered number by one keystroke. LNR is
repeatable after each off-hook. The LNR key also supports the sliding cursor protocol (see pt. 10) to allow
convenient redialing with PABX systems.
8.4 Pause key (PAUSE)
This key is to insert a pause in a digit string. Each pause is 2 seconds if inserted within the first 5 digits otherwise a
wait function will halt dialling until a PS or LNR key is depressed.
8.5 Tone / Pulse switching
When any of the LD dialing modes is selected (see pt. 7.3), a switch to temporary MF can be performed by
pressing the ! key to get into DTMF mode and one of the flash (R)-keys to get back to pulse dialing. Once in MF
mode the mode output LED is active.
Remark: temporary MF can only be activated, when the initial dialing mode selected by J2 (see pt. 7.3) is in one of
the pulse dialing modes.
8.6 Enter/M5
The ENTER key is used to program the memory (M5). Pressing ENTER followed by the key M5 opens the memory
location for storing the number.
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