AD9736BBC datasheet(21/42 Pages) AD

21 / 42 page

Preliminary Technical Data

AD9736/AD9735/AD9734

Rev. PrJ | Page 21 of 42

configurations or initiating a software reset is highly

recommended. In the event of unexpected programming sequences

the AD9736 SPI may become inaccessible. For example, if user

code inadvertently changes the LONG_INS bit or LSBFIRST bit the

following bits may have unexpected results. The SPI can be

returned to a known state by writing an incomplete byte (1-7 bits)

of all zeroes followed by three bytes of 0x00. This will return to

MSB first short instructions (REG00 = 0x00) so the device may be

reinitialized.

R/W N0N1

A0 A1

A3 A4D7 D6N D5N

D00

D10

D20

D30

D7 D6N D5N

D00

D10

D20

D30

INSTRUCTION CYCLE

DATA TRANSFER CYCLE

CSB

SCLK

SDIO

SDO

Figure 19. Serial Register Interface Timing MSB First

INSTRUCTION CYCLE

DATA TRANSFER CYCLE

CSB

SCLK

SDIO

SDO

A3 A4

N0 R/W D0 D10 D20

D7N

D6N

D5N

D4N

D0D10 D20

D7N

D6N

D5N

D4N

Figure 20. Serial Register Interface Timing LSB First

INSTRUCTION BIT 6

INSTRUCTION BIT 7

CSB

SCLK

SDIO

tDS

tDH

tPWH

tPWL

tSCLK

Figure 21. Timing Diagram for SPI Register Write

DNV

CSB

SCLK

SDIO

Figure 22. Timing Diagram for SPI Register Read

After the last instruction bit is written to the SDIO pin the driving

signal must be set to a high impedance in time for the bus to turn

around. The serial output data from the AD9736 will be enabled by

the falling edge of SCLK. This causes the first output data bit to be

shorter than the remaining data bits as shown in Figure 22.

PIN MODE OPERATION

When the PIN_MODE input (pin L1) is set high, the SPI port is

disabled. The SPI port pins are remapped as shown in Table 10. The

function of these pins is described in Table 11. The remaining

PIN_MODE register settings are shown in Table 5, the SPI register

map.

Pin Number

PIN_MODE = 0

PIN_MODE = 1

E13

IRQ

UNSIGNED

F13

CSB

G13

SCLK

FSC0

E14

RESET

F14

SDIO

FIFO

G14

SDO

FSC1

Table 10. SPI_MODE vs. PIN_MODE Inputs

Function

UNSIGNED

0, Two’s complement input data format

1, Unsigned input data format

0, Interpolation disabled

1, Interpolation = 2x enabled

FSC1, FSC0

00, Sleep mode

01, 10mA full scale output current

10, 20mA full scale output current

11, 30mA full scale output current

0, Chip enabled

1, Chip in power down state

FIFO

0, Input FIFO disabled

1, Input FIFO enabled

Table 11. PIN_MODE Input Functions

Care must be taken when using PIN_MODE since only the control

bits shown in Table 11 can be changed. If the remaining register

default values are not suitable for the desired operation

PIN_MODE cannot be used.

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