REV. 0

AD5532

–13–

OFFSET SEL

A4 –A0

CAL

0

0

MSB

LSB

MODE BIT 1

MODE BIT 2

MODE BITS

0

TEST BIT

a. 10-Bit Input Serial Write Word (SHA Mode)

OFFSET SEL

A4 –A0

CAL

1

0

MSB

LSB

MODE BITS

DB1 3 –DB0

0

TEST BIT

b. 24-Bit Input Serial Write Word (DAC Mode)

OFFSET SEL

A4 –A0

CAL

0

1

MSB

LSB

MODE BITS

DB1 3 –DB0

0

TEST BIT

10-BIT

SERIAL WORD

WRITTEN TO PART

14-BIT DATA

READ FROM PART AFTER

NEXT FALLING EDGE OF

SYNC

(DB13 = MSB OF DAC WORD)

MSB

LSB

c. Input Serial Interface (Acquire and Readback Mode)

OFFSET SEL

A4 –A0

CAL

1

1

MSB

LSB

MODE BITS

DB1 3 –DB0

0

TEST BIT

10-BIT

SERIAL WORD

WRITTEN TO PART

14-BIT DATA

READ FROM PART AFTER

NEXT FALLING EDGE OF

SYNC

(DB13 = MSB OF DAC WORD)

MSB

LSB

d. Input Serial Interface (Readback Mode)

Figure 19. Serial Interface Formats

DB13–DB0

These are used to write a 14-bit word into the addressed DAC

register. Clearly, this is only valid when in DAC mode.

The serial interface is designed to allow easy interfacing to

most microcontrollers and DSPs, e.g., PIC16C, PIC17C, QSPI,

SPI, DSP56000, TMS320, and ADSP-21xx, without the need

for any glue logic. When interfacing to the 8051, the SCLK

must be inverted. The Microprocessor/Microcontroller Interface

section explains how to interface to some popular DSPs and

microcontrollers.

Figures 3, 4, and 5 show the timing diagram for a serial read and

write to the AD5532. The serial interface works with both a con-

tinuous and a noncontinuous serial clock. The first falling edge of

SYNC resets a counter that counts the number of serial clocks to

ensure the correct number of bits are shifted in and out of the

serial shift registers. Any further edges on

SYNC are ignored until

the correct number of bits are shifted in or out. Once the correct

number of bits for the selected mode have been shifted in or out,

the SCLK is ignored. In order for another serial transfer to take

place the counter must be reset by the falling edge of

SYNC.

In readback, the first rising SCLK edge after the falling edge of

SYNC causes D

state on the falling edge of the fourteenth SCLK. Data on the

falling edge of the

SYNC signal and on subsequent SCLK fall-

will not shift data in or out until it receives the falling edge of

the

SYNC signal.

Parallel Interface (SHA Mode Only)

The SER/

PAR bit must be tied low to enable the parallel inter-

face and disable the serial interface. The parallel interface is

controlled by 9 pins.

CS

Active low package select pin. This pin is shared with the

SYNC

function for the serial interface.

WR

Active low write pin. The values on the address pins are latched

on a rising edge of

WR.

A4–A0

Five address pins (A4 = MSB of address, A0 = LSB). These are

used to address the relevant channel (out of a possible 32).

Offset_Sel

Offset select pin. This has the same function as the Offset_Sel

bit in the serial interface. When it is high, the offset channel is

addressed. The address on A4–A0 is ignored in this case.

Cal

The acquisition time is then 45

µs (typ) and accuracy may be

reduced.