Holtek HT827A0 Manual page 19

Sampling rate counter
The HT827A0 offers a sampling rate counter.
This counter contains a 5 bit programmable
count-up counter. The clock may come from
128kHz or 2kHz by code option and the clock
base on 3.579545MHz system clock.
Bit
Labels Function
s
SR0~ To define a voice sampling
0~4
SR4 rate or envelope decaying time
2K/ To define an input clock
5
128K source (0=128K; 1=2K)
¾ 6~7 Unused bits, read as ²0²
SRC register
1 2 8 K
S a m p l i n g R a t e
C o u n t e r
P r e l o a d R e g i s t e r
2 K
S a m p l i n g R a t e
C o u n t e r
2 K / 1 2 8 K S R O N
Sample rate counter
When the 128kHz clock is selected, 26 kinds of
sampling rate are provided for a voice synthe-
sizer. The following is a table of the 26 kinds of
sampling rates:
Code Freq. Code
xx00 0000 3.50kHz xx00 1101 5.89kHz
xx00 0001 3.61kHz xx00 1110 6.21kHz
xx00 0010 3.72kHz xx00 1111 6.58kHz
xx00 0011 3.86kHz xx01 0000 6.99kHz
xx00 0100 3.99kHz xx01 0001 7.46kHz
xx00 0101 4.14kHz xx01 0010 7.99kHz
xx00 0110 4.30kHz xx01 0011 8.61kHz
xx00 0111 4.48kHz xx01 0100 9.32kHz
xx00 1000 4.66kHz xx01 0101 10.17kHz
xx00 1001 4.86kHz xx01 0110 11.19kHz
Code
xx00 1010 5.08kHz
xx00 1011 5.33kHz
xx00 1100 5.59kHz
Note: ²xx² means don¢t care
On the other hand, when the 2kHz clock is cho-
sen, 32 kinds of time periods of the envelope de-
cay is offered.
The following is a table of the envelope decay:
Code
xx10 0000 54.6Hz
xx10 0001 56.4Hz
D A T A
xx10 0010 58.3Hz
B U S
R E L O A D
xx10 0011 60.3Hz
xx10 0100 62.4Hz
xx10 0101 64.7Hz
¸ 1
C o u n t e r
xx10 0110 67.2Hz
O V E R F L O W
t o I n t e r r u p t
xx10 0111 69.9Hz
xx10 1000 72.8Hz
xx10 1001 76.0Hz
xx10 1010 79.5Hz
xx10 1011 83.2Hz
Freq.
xx10 1100 87.4Hz
xx10 1101 92.0Hz
xx10 1110 97.1Hz
xx10 1111 102.8Hz xx11 1111
Note: ²xx² means don¢t care
19
HT827A0
Freq. Code Freq.
xx01 0111 12.43kHz
xx01 1000 13.98kHz
xx01 1001 15.98kHz
Sampling rate table
Freq. Code Freq.
xx11 0000 109.3Hz
xx11 0001 116.5Hz
xx11 0010 124.9Hz
xx11 0011 134.5Hz
xx11 0100 145.7Hz
xx11 0101 158.9Hz
xx11 0110 174.8Hz
xx11 0111 194.2Hz
xx11 1000 218.5Hz
xx11 1001 249.7Hz
xx11 1010 291.3Hz
xx11 1011 349.6Hz
xx11 1100 437.0Hz
xx11 1101 582.7Hz
xx11 1110 874.0Hz
1.75kHz
Envelope decay table
March 15, 2000