參數(shù)資料
型號: AD2S90AP
廠商: Analog Devices Inc
文件頁數(shù): 11/12頁
文件大?。?/td> 0K
描述: IC R/D CONV 12BIT 20-PLCC
標(biāo)準(zhǔn)包裝: 1
類型: R/D 轉(zhuǎn)換器
輸入類型: 并聯(lián)
輸出類型: 數(shù)字
接口: 串行
電流 - 電源: 10mA
安裝類型: 表面貼裝
封裝/外殼: 20-LCC(J 形引線)
供應(yīng)商設(shè)備封裝: 20-PLCC(9x9)
包裝: 管件
AD2S90
REV. D
–8–
Select the AD2S90 and frame the data. The S1 register is fixed
at 16 bits, therefore, to obtain the 12-significant bits the proces-
sor needs to execute four right shifts. Once the NEC7720 has
read 16 bits, an internal interrupt is generated to read the inter-
nal contents of the S1 register.
SCLK
SIEN
S1
SCLK
CS
DATA
PD7720
AD2S90
NOTE:
ADDITIONAL PINS OMITTED FOR CLARITY
Figure 13.
PD7720/AD2S90 Serial Interface
EDGE TRIGGERED 4
DECODING LOGIC
In most data acquisition or control systems the A, B incremental
outputs must be decoded into absolute information, normally a
parallel word, before they can be utilized effectively.
To decode the A, B outputs on the AD2S90 the user must
implement a 4
× decoding architecture. The principle states that
one A, B cycle represents 4 LSB weighted increments of the
converter (see Equation 4).
Up = (
↑A) B + (↓B) A + (↓A) B + (↑
Β) A
Down = (
↑A) B + (↑B) A + (↓A) B + (↓B) A
(4)
CLOCKWISE ROTATION
COUNTER CLOCKWISE ROTATION
UP
DOWN
CH A
CH B
Figure 14. Principles of 4
× Decoding
The algorithms in Equation 4 can be implemented using the
architecture shown in Figure 15. Traditionally the direction of
the shaft is decoded by determining whether A leads B. The
AD2S90 removes the need to derive direction by supplying a
direction output state which can be fed straight into the up-
down counter.
For further information on this topic please refer to the applica-
tion note “Circuit Applications of the AD2S90 Resolver-to-
Digital Converters.”
TMS32020 Interfacing
Figure 11 shows the serial interface between the AD2S90 and
the TMS32020. The interface is configured in alternate internal
framing, external clock (externally inverted) mode. Sixteen bits
of data are clocked from the AD2S90 into the data receive regis-
ter (DRR) of the TMS32020. The DRR is fixed at 16 bits. To
obtain the 12-significant bits, the processor needs to execute
three right shifts. (First bit read is void, the last three will be
zeros). When 16 bits have been received by the TMS32020, it
generates an internal interrupt to read the data from the DRR.
SCLK
FSR
DRR
SCLK
CS
DATA
TMS32020
AD2S90
NOTE:
ADDITIONAL PINS OMITTED FOR CLARITY
Figure 11. TMS32020/AD2S90 Serial Interface
DSP56000 Interface
Figure 12 shows a serial interface between the AD2S90 and the
DSP56000. The DSP in configured for normal mode synchro-
nous operation with gated clock with SCLK and SC1 as out-
puts. SC1 is applied to
CS.
SCLK
SC1
SRD
SCLK
CS
DATA
DSP56000
AD2S90
NOTE:
ADDITIONAL PINS OMITTED FOR CLARITY
Figure 12. DSP56000/AD2S90 Serial Interface
The DSP56000 assumes valid data on the first falling edge of
SCLK. SCLK is inverted to ensure that the valid data is clocked
in after one leading bit. The receive data shift register (SRD) is
set for a 13-bit word.
When this register has received 13 bits of data, it generates an
internal interrupt on the DSP56000 to read the 12 bits of sig-
nificant data from the register.
NEC7720 Interface
Figure 13 shows the serial interface between the NEC7720 and
the AD2S90. The NEC7720 expects data on the rising edge of
its SCLK output, and therefore unlike the previous interfaces no
inverter is required to clock data into the S1 register. There is
no need to ignore the first data bit read.
SIEN is used to Chip
EDGE GENERATOR
A
B
CHA
CHB
DIRECTION
CLOCK
U/D
RESET
UP/DOWN
COUNTER
PARALLEL
DIGITAL
OUTPUT
Figure 15. 4
× Decoding Incremental to Parallel Conversion
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