參數資料
型號: HD404654S
廠商: Hitachi,Ltd.
英文描述: 4-Bit Single-Chip Microcomputer
中文描述: 4位單片機
文件頁數: 78/109頁
文件大小: 430K
代理商: HD404654S
HD404654 Series
78
DTMF Generator Circuit
The MCU provides a dual-tone multifrequency (DTMF) generator circuit. The DTMF signal consists of
two sine waves to access the switching system.
Figure 63 shows the DTMF keypad and frequencies. Each key enables tones to be generated corresponding
to each frequency. Figure 64 shows a block diagram of the DTMF circuit.
The OSC clock (400 kHz, 800 kHz, 2 MHz, 3.58 MHz or 4 MHz) is changed into four clock signals
through the division circuit (1/2, 1/5, 1/9 and 1/10). The DTMF circuit uses one of the four clock signals,
which is selected by system clock select register 1 (SSR1: $029) and system clock select register 2 (SSR2:
$02A) depending on the OSC clock frequency. The DTMF circuit has transformed programmable dividers,
sine wave counters, and control registers.
The DTMF generation circuit is controlled by the following three registers.
1
2
3
A
4
5
6
B
7
8
9
C
*
0
#
D
R1 (697 Hz)
R2 (770 Hz)
R3 (852 Hz)
R4 (941 Hz)
C
C
C
C
Figure 63 DTMF Keypad and Frequencies
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相關代理商/技術參數
參數描述
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