REV. A

AD5533B

–13–

DB13–DB0 Bit

These are used in both readback modes to read a 14-bit word

from the addressed DAC register.

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 and 4 show the timing diagram for a serial read and

write to the AD5533B. The serial interface works with both a

continuous 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 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

first SCLK falling edge after the falling edge of the

SYNC signal

and on subsequent SCLK falling edges. The serial interface will

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

SYNC signal.

*SPI and QSPI are trademarks of Motorola, Inc.

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 (ISHA 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

b. Input Serial Interface (Acquire and Readback Mode)

OFFSET SEL

A4–A0

0

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

c. Input Serial Interface (Readback Mode)

Figure 8. Serial Interface Formats

Parallel Interface

The SER/

PAR bit is tied low to enable the parallel interface and

disable the serial interface. The parallel interface is controlled

by nine pins as follows:

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 and the address on A4–A0 is ignored.

Cal

Same functionality as the Cal bit in the serial interface. When

MICROPROCESSOR INTERFACING

AD5533B to ADSP-21xx Interface

The ADSP-21xx family of DSPs is easily interfaced to the

AD5533B without the need for extra logic.

A data transfer is initiated by writing a word to the TX register

after the SPORT has been enabled. In a write sequence, data is

clocked out on each rising edge of the DSP’s serial clock and

clocked into the AD5533B on the falling edge of its SCLK. In