AK2401 Datasheet, PDF (52/103 Pages) Asahi Kasei Microsystems – Direct Conversion Transceiver

[AK2401]
■ Coefficient Write
A coefficient is written to the programmable FIR filter via the CSN, SCLK and SDATAI pins. COEF_ST bit
= “1” <Address 0x2D> sets these three pins to programmable FIR filter coefficient write mode. During the
coefficient write mode, COEF_ST bit is kept to “1” and 16-bit coefficient data is written sequentially for the
number of time set by COEF_NUM[6:0] bits. COEF_ST bit returns to “0” automatically and coefficient
write mode is finished after writing the coefficient for designated number of times. Normal register access
will be available when the coefficient write mode is finished.
If the setting value of COEF_NUM[6:0] bits is smaller than the maximum tap number, rest of the tap
coefficient will be filled by “0”. If the setting value of COEF_NUM[6:0] bits is larger than the maximum tap
number, internal limit process is executed automatically. Therefore, coefficient write cannot be executed
more than the maximum tap number. When COEF_NUM[6:0] bits are set to “0000000”, the AK2401 will
not enter coefficient write mode even if COEF_ST bit is set to “1”.
Programmable FIR filter setting example and write sequence are shown below (Figure 33).
(1) Write a start register of the coefficient write. The following shows the setting of this example.
{W/R, Address, COEF_NUM[6:0], COEF_ST} = {0010 0100 1000 0011}
TAP0 ~ TAP64, coefficient will be written 65 taps in total since COEF_NUM[6:0] bits are set to
65(dec).
(2) Register interface becomes coefficient write mode after writing the start bit (1). In this example,
65 coefficients are written sequentially. From a coefficient only register TAP0 until TAP64, 16-bit
data are written sequentially and the coefficient write mode will be finished. COEF_ST bit will
returns to “0” automatically when the coefficient write mode is finished.
(3) It is recommended to set COEF_NUM[6:0] bits “0000000” after writing coefficient to prevent
unintended change of the setting.
(4) After the coefficient write mode, the AK2401 enters normal register write mode. A written
coefficient can be readback in normal register access. Access to <Address 0x38 ~ 0x39> to
readback the register values. First, coefficient TAP that is desired to readback must be set to
TAP_NUM[6:0] bits <Address 0x37>. In this case, TAP_NUM[6:0] bits = “1000000”= 64(dec),
therefore the coefficient of TAP64 is readout. Higher 8-bit of the assigned TAP coefficient is
readback to R_COEF[15:8] bits <Address 0x38> and lower 8-bit is readback to R_COEF[7:0]
bits <Address 0x39>.
(1) ^Start
(2) Write Coefficient
(3) Read Coefficient
COEF_ST
CSN
SCLK
SDATAI
SDATAO
0 0x2D 0x41
TAP0
COEF0[15:0]
TAP1
COEF1[15:0]
TAP64
COEF64[15:0]
0 0x37 0x40
1 0x38
COEF64
[15:8]
1 0x39
COEF64
[7:0]
◆^{Register for Coefficient}
Upper
8bit
TAP0
COEF0[15:0]
TAP1
COEF1[15:0]
・・・
TAP64
TAP65
TAP74
COEF64[15:0]
0x0000
・・・
0x0000
All TAPs exceeds COEF_NUM[6:0] bits setting will be filled by “0”
(In this figure, TAP65-74 are filled by “0” since COEF_NUM[6:0] bits =65(dec))
Figure 33. Programmable FIR Filter Write Example
Lower
8bit
017003093-E-00
52
2017/3