AD1845 Analog Devices, AD1845 Datasheet - Page 25

• Manufacturer Part Number: AD1845
• Description: Parallel-port 16-Bit Soundport Stereo Codec
• Manufacturer: Analog Devices

REV. B
TL7:0
This register’s initial state after reset is “0000 0000.”
TU7:0
This register’s initial state after reset is “0000 0000.”
FU7:0
This register’s initial state after reset is “0001 1111.”
FL7:0
This register’s initial state after reset is “0100 0000.”
Lower Timer Bits Register (IXA3:0 = 20)
Upper Timer Bits Register (IXA3:0 = 21)
Upper Frequency Select Bits Register (IXA3:0 = 22)
Lower Frequency Select Bits Register (IXA3:0 = 23)
IXA3:0
IXA3:0
IXA3:0
IXA3:0
20
21
22
23
Lower Timer Bits. This byte is the lower byte of the timer register containing the eight least significant bits of the
16-bit register. Reads from this register return the same value which was written. The current timer value con-
tained in the counters cannot be read.
Upper Timer Bits. This byte is the upper byte of the timer register containing the eight most significant bits of the
16-bit register. Reads from this register return the same value which was written. The current timer value con-
tained in the counters cannot be read. The timer counter is determined by the clock source selected (see below).
Input Frequency
24.576 MHz
14.31818 MHz
24.000 MHz
25.000 MHz
33.000 MHz
Upper Frequency Select Bits. This register is accessible when FREN is 1. Writing to this register allows the user
to program the sampling frequency from 4 kHz to 50 kHz in 1 Hz increments. Writing to the Lower and Upper
Frequency Select Register allows the AD1845 to process audio data using approximately 50,000 different audio
sample rates. One LSB represents exactly one hertz. Selecting frequencies below 4 kHz or above 50 kHz will
result in degraded audio performance. Some common sample rates are listed below:
Quality
Voice
Radio
Tape
CD
DAT
Lower Frequency Select Bits. Writing to the Lower Frequency Select register updates the entire 16-bit frequency register.
Data 7
Data 7
Data 7
Data 7
TU7
FU7
TL7
FL7
Sampling Frequency
8.0 kHz
11.025 kHz
22.05 kHz
44.1 kHz
48.0 kHz
Data 6
Data 6
Data 6
Data 6
TU6
FU6
TL6
FL6
Divider
247
144
242
252
333
Data 5
Data 5
Data 5
Data 5
TU5
TL5
FU5
FL5
–25–
Timer Counter
10.050 s
10.057 s
10.083 s
10.080 s
10.091 s
FU7:0 (hex)
0001 1111
0010 1011
0101 0110
1010 1100
1011 1011
Data 4
Data 4
Data 4
Data 4
TU4
FU4
TL4
FL4
Data 3
Data 3
Data 3
Data 3
TU3
FU3
TL3
FL3
FL7:0 (hex)
0100 0000
0001 0001
0010 0010
0100 0100
1000 0000
Data 2
Data 2
Data 2
Data 2
TU2
FU2
TL2
FL2
Data 1
default
Data 1
Data 1
Data 1
TU1
FU1
TL1
FL1
AD1845
Data 0
Data 0
Data 0
Data 0
TU0
TL0
FU0
FL0