CS5516-ASZ datasheet(19/41 Pages) CIRRUS

19 / 41 page

Reading a register in the converter requires a

command word to be written to the SID pin.

For example, to read the conversion data regis-

ter, the following command sequence should be

performed. First, the command word 88(H)

would be issued to the port. In the 5 wire inter-

face mode, this would involve activating CS

low, followed by 8 SCLKs (note that SCLK

must always start low and transition from low to

high to latch the transmit data, and then back

low again) to input the 8-bit command word. CS

must be low for the serial port to recognize

SCLKs during a write or a read, but it is actually

the first rising SCLK during command time that

gives the user control over the port. After writ-

ing the command word, the user must pause and

wait until the CS5520 presents the selected reg-

ister data to the serial port. The DRDY signal

will fall when the data is available. When read-

ing the conversion data register, it may take up

to 112,000 XIN clock cycles for DRDY to fall

after the 88(H) command word is recognized.

See Figure 4 for an illustration of command and

data word timing.

The conversion data register is actually the accu-

mulator of the post-processor which computes

the output data. At the end of each filter convo-

lution cycle, the internal microcontroller checks

to see if a read conversion data register com-

mand has been interpreted. If so, it transfers the

accumulator result to the serial port.

Whenever registers other than the conversion

data register are read, the DRDY pin will fall

within 256 XIN clock cycles (62.5

µs with

XIN = 4.096 MHz) after the command word is

recognized. When DRDY falls, 24 SCLKs are

then issued to the port to read the 24-bit output

data word. DRDY will return high after all 24

bits have been clocked out. The SOD pin will be

in a Hi-Z state whenever CS is high, or after all

24 output data bits have been clocked out of the

port.

The CS5516/20 is designed such that it can out-

put conversion data words continuously, without

issuing a new command word prior to each data

read. Under the following circumstances, con-

tinuous conversion data can be read from the

port after issuing only one 88(H) command

word. Once the command to read the conversion

data register is issued, DRDY must be allowed

to go low, after which 24 SCLKs are issued to

read the data. This will cause DRDY to return

high.

The converter will continue to output conversion

words at the update rate as long as a different

command word is not started prior to DRDY

falling again. The user is not required to read

every output word to remain in the continuous

update mode. DRDY will toggle high, and then

low as each new output word becomes available.

If a command word is issued immediately after a

data word is read, the converter will end the read

conversion mode. Figure 5 illustrates the con-

tinuous data mode.

The user should perform all data reads and com-

mand writes within 51,000 XIN clock cycles

after DRDY falls to avoid ambiguity as to who

controls the serial port.

If SMODE = 1 (tied to VD+), the interface oper-

ates as a 3 wire interface using only SOD, SID,

and SCLK. In the 3 wire mode CS must be tied

to DGND. DRDY operates normally but is not

used.

Instead, the DRDY signal modifies the

behavior of the SOD signal, allowing it to signal

to the user when data is available. To read data

from the converter requires a command word to

be written to the SID pin. The SOD output is

normally high (never Hi-Z). When output data

is available, the SOD signal will go low. The

user would then issue 8 SCLKs to the SCLK pin

to clear this data ready signal.

On the falling

edge of the 8th SCLK the SOD pin will present

the first bit of the 24-bit output word. 24 SCLKs

are then issued to read the data. Then SOD will

go high. SID should remain low whenever the

CS5516, CS5520

DS74F1

DS74F2

CS5516-ASZ Datasheet(PDF) 19 Page - Cirrus Logic

CS5516-ASZ Datasheet(HTML) 19 Page - Cirrus Logic

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

Datasheet Download

Link URL