GC3011 Datasheet, PDF (18/35 Pages) Texas Instruments – DIGITAL RESAMPLER

GC3011 DIGITAL RESAMPLER
4.1 RATIO WORD REGISTERS
Registers 0, 1, 2, and 3 contain the 32 bit resampling ratio word. Bit 0 is the LSB, bit 31 is the MSB.
ADDRESS 0:
RATIO BYTE 0
BIT
TYPE
0-7
R/W
NAME
RATIO[0:7]
ADDRESS 1:
RATIO BYTE 1
BIT
TYPE
0-7
R/W
NAME
RATIO[8:15]
ADDRESS 2:
RATIO BYTE 2
BIT
TYPE
0-7
R/W
NAME
RATIO[16:23]
ADDRESS 3:
RATIO BYTE 3
BIT
TYPE
0-7
R/W
NAME
RATIO[24:31]
DESCRIPTION
Byte 0 (least significant) of the ratio
DESCRIPTION
Byte 1 of the ratio
DESCRIPTION
Byte 2 of the ratio
DESCRIPTION
Most significant byte of the ratio
If the desired output sampling rate is F_OUT, and the input sampling rate is F_IN, then the resampling
ratio should be set to:
RATIO = F_IN/F_OUT
Where RATIO is a unsigned fractional value ranging from 1 to 4 and formatted as follows:
BYTE 3
MSB
BYTE 2
BYTE 1
BYTE 0
LSB
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
INTEGER
FRACTION
BINARY
POINT
Bits 30 and 31 are the integer part of RATIO and must equal 1, 2, or 3. An integer portion of 0 will
not work. The fractional part can take on any value.
After loading the resampling ratio value the user can choose, using the LOAD_RATIO control bits
in the Sync Mode register (See Section 4.4), to have it take effect immediately, or when a sync event occurs.
GRAYCHIP,INC.
- 18 -
JULY 22, 1996
This document contains information which may be changed at any time without notice