AD9516-2SLASHPCBZ datasheet(53/84 Pages) AD

53 / 84 page

AD9516-2

Rev. 0 | Page 53 of 84

Read

If the instruction word is for a read operation, the next N × 8

SCLK cycles clock out the data from the address specified in the

instruction word, where N is 1 to 3 as determined by W1:W0.

If N = 4, the read operation is in streaming mode, continuing

until CS is raised. Streaming mode does not skip over reserved

or blank registers. The readback data is valid on the falling

edge of SCLK.

The default mode of the AD9516 serial control port is the

bidirectional mode. In bidirectional mode, both the sent data

and the readback data appear on the SDIO pin. It is also possible to

set the AD9516 to unidirectional mode (SDO enable register,

0x00<7>). In unidirectional mode, the readback data appears

on the SDO pin.

A readback request reads the data that is in the serial control

port buffer area, or the data in the active registers (see Figure 61).

Readback of the buffer or active registers is controlled by 0x04<0>.

The AD9516 supports only the long instruction mode;

therefore, 0x00<4:3> must be set to 11b (this register uses

mirrored bits). Long instruction mode is the default at power-

up or reset.

The AD9516 uses Register Address 0x000 to Register

Address 0x232.

SCLK

SDIO

SDO

SERIAL

CONTROL

PORT

UPDATE

REGISTERS

WRITE REGISTER 0x232 = 0x01

TO UDATE REGISTERS

Figure 61. Relationship Between Serial Control Port Buffer Registers and

Active Registers of the AD9516

THE INSTRUCTION WORD (16 BITS)

The MSB of the instruction word is R/W, which indicates

whether the instruction is a read or a write. The next two bits,

W1:W0, indicate the length of the transfer in bytes. The final

13 bits are the address (A12:A0) at which to begin the read or

write operation.

For a write, the instruction word is followed by the number of

bytes of data indicated by Bits W1:W0, see Table 47.

Table 47. Byte Transfer Count

Bytes to Transfer

Streaming mode

A12:A0

: These 13 bits select the address within the register map

that is written to or read from during the data transfer portion

of the communications cycle. Only Bits<A9:A0> are needed to

cover the range of the 0x232 registers used by the AD9516.

Bits<A12:A10> must always be 0b. For multibyte transfers, this

address is the starting byte address. In MSB first mode,

subsequent bytes increment the address.

MSB/LSB FIRST TRANSFERS

The AD9516 instruction word and byte data can be MSB first

or LSB first. Any data written to 0x00 must be mirrored, the

upper four bits (<7:4>) must be mirrored with the lower four

bits (<3:0>). This makes it irrelevant whether LSB first or MSB

first is in effect. As an example of this mirroring, see the default

setting for this register: 0x00, which mirrors Bit 4 and Bit 3.

This sets the long instruction mode (default, and is the only

mode supported).

The default for the AD9516 is MSB first.

When LSB first is set by 0x00<2> and 0x00<6>, it takes effect

immediately, because it only affects the operation of the serial

control port and does not require that an update be executed.

When MSB first mode is active, the instruction and data bytes

must be written from MSB to LSB. Multibyte data transfers in

MSB first format start with an instruction byte that includes the

data bytes must follow in order from the high address to the low

address. In MSB first mode, the serial control port internal

address generator decrements for each data byte of the

multibyte transfer cycle.

When LSB first is active, the instruction and data bytes must be

written from LSB to MSB. Multibyte data transfers in LSB first

format start with an instruction byte that includes the register

address of the least significant data byte followed by multiple

data bytes. The internal byte address generator of the serial

control port increments for each byte of the multibyte

transfer cycle.

The AD9516 serial control port register address decrements

from the register address just written toward 0x00 for multibyte

I/O operations if the MSB first mode is active (default). If the

LSB first mode is active, the register address of the serial control

port increments from the address just written toward 0x232 for

multibyte I/O operations.

Streaming mode always terminates when it hits Address 0x232.

Note that unused addresses are not skipped during multibyte

I/O operations.

Table 48. Streaming Mode (No Addresses Are Skipped)

Write Mode

Address Direction

Stop Sequence

LSB first

Increment

0x230, 0x231, 0x232, stop

MSB first

Decrement

0x001, 0x000, 0x232, stop

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