EM73962A
4-BIT MICROCONTROLLER
Volume control register
The are 8 levels of volume for sound generator. P17 is the volume control register.
Port17
Initial value : * 1111
3
*
2
1
0
VCR
VCR
ts/tp
8/8
7/8
6/7
5/8
4/8
3/8
2/8
1/8
1
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
ts
1
1
1
0
0
0
0
tp
1
tp=
60KHz
PROGRAM EXAMPLE:
LDIA
#1001B ; basic frequency : 60 KHz tone output
OUTA
LDIA
P30
#0011B ; 600 Hz tone output
OUTA
LDIA
OUTA
P24
#0001B
P23
RESETTING FUNCTION
When CPU in normal working condition and RESET pin holds in low level for three instruction cycles at least,
then CPU begins to initialize the whole internal states, and when RESET pin changes to high level, CPU begins
to work in normal condition.
The CPU internal state during reset condition is as following table :
Hardware condition in RESET (f1) state
Program counter
Initialvalue
0000h
Status flag
01h
Interrupt enable flip-flop ( EI )
MASK0 ,1, 2, 3
00h
00h
Interrupt latch ( IL )
P3, P9, 16, 25, 27, 28, 29, 30
P4, 8, 17, 23, 24
00h
00h
0Fh
RC oscillator
Startoscillation
The RESET pin is a hysteresis input pin and it has a pull-up resistor available by mask option.
The simplest RESET circuit is connect RESET pin with a capacitor to VSS and a diode to VDD.
RESET
* This specification are subject to be changed without notice.
10.8.2001
22
ELAN [ ELAN MICROELECTRONICS CORP ]
