W921E840A Datasheet, PDF (25/58 Pages) Winbond – 4-BIT MICROCONTROLLER

W921E840A/W921C840
The output frequency of the row and column will be controlled by the row/column frequency control
register (RCCTL).
RCCTL register: (address = 015H, default data = 0H)
b3
b2
b1
b0
Reserved
0: Row frequency disable
1: Row frequency enable
0: Column frequency disable
1: Column frequency enable
0: DTMF disable (H-Z)
1: DTMF enable
The following table shows the DTMF keypad and its frequency.
C1 C2 C3 C4
1 2 3 A R1
4 5 6 B R2
7 8 9 C R3
*
0
#
D R4
Key Frequency
R1
697 Hz
R2
770 Hz
R3
852 Hz
R4
941 Hz
C1 1209 Hz
C2 1336 Hz
C3 1477 Hz
C4 1633 Hz
6.8 Beep Tone Generator
There are four kinds of frequency that can output from the BTG pin that works as beep tone
generator. The BTG pin can output the special frequency2 KHz, 1 KHz, 630 Hz or 520 Hz, and the
correct output frequency is decided by the OSCCTR register (address = 013H) and BTGR register
(address = 03FH) as shown below:
BTGR register: (address = 03FH, default data = 0H)
b3
b2
b1
b0
Reserved
b1 b0
00
01
10
11
Output Freq.
2K Hz
1K Hz
630 Hz
520 Hz
0: Disable beep tone generator
(BTG pin keep in high state)
1: Enable beep tone generator
If the beep tone generator is disabled by setting bit 3 of the BTGR register to zero or after power on
reset, the BTG output pin will remain in high state.
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Publication Release Date: July 1999
Revision A3