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BUS BUSY

SYNC_O

CLK_O

RD

1F

1R

2R

18F

SDO

D15

D14

D0

See Figures 5 and 6

See Figures 7 and 8

18R

DATA READ IN BYTE MODE

BUS BUSY

SYNC_O

CLK_O

RD

1F

1R

2R

18F

SDO

D15

D14

D7

D0

18R

9R

9F

10R

D8

ADS8413

SLAS490 – OCTOBER 2005

Figure 3. Data Read With CS Low and BYTE = 0

As shown in Figure 3, a new data read cycle is initiated with the falling edge of RD, if CS is low and the device is

in a wait or sample phase. The device releases the LVDS o/p (SYNC_O, SDO) from 3-state and sets

BUS_BUSY high at the start of the read cycle. The SYNC_O cycle is 16 clocks wide (rising edge to rising edge)

if BYTE i/p is held low and can be used to synchronize a data frame. The clock count begins with the first CLK_O

falling edge after a SYNC_O rising edge. The MSB is latched out on the second rising edge (2R) and each

subsequent data bit is latched out on the rising edge of the clock. The receiver can shift data bits on the falling

edges of the clock. The next rising edge of SYNC_O coincides with the 16th rising edge of the clock. D0 is

latched out on the 17th rising edge of the clock. The receiver can latch the de-serialized 16-bit word on the 18th

rising edge (18R, or the second rising edge after a SYNC_O rising edge).

CS high during a data read 3-states SYNC_O and SDO. These signals remain in 3-state until the start of the

next data read cycle.

Byte mode is selected by setting BYTE = 1, this mode is allowed for any condition listed in Table 1. Figure 4

shows a data read operation in byte mode.

Figure 4. Data Read Timing Diagram with CS Low and BYTE = 1

Similar to Figure 3, a new data read cycle is initiated with the falling edge of RD, if CS is low and device is in a

wait or sample phase. The device releases the LVDS o/p (SYNC_O, SDO) from 3-state and sets BUS_BUSY

high at the start of the read cycle. The SYNC_O cycle is 8 clocks wide (rising edge to rising edge) if BYTE i/p is

held high and can be used to synchronize a data frame. The clock count begins with the first CLK_O falling edge

after a SYNC_O rising edge. The MSB is latched out on the second rising edge (2R) and each subsequent data

bit is latched out on the rising edge of the clock. The receiver can shift data bits on the falling edges of clock. The

next rising edge of SYNC_O coincides with the 8th rising edge of the clock. D8 is latched out on the 9th rising

edge of the clock. The receiver can latch the de-serialized higher byte on the 10th rising edge (10R, or second

rising edge after a SYNC_O rising edge). The de-serialized lower byte can be latched on the 18th rising edge

(18R).

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