AD9148BPCZ AD [Analog Devices], AD9148BPCZ Datasheet - Page 21

• Manufacturer Part Number: AD9148BPCZ
• Description: Quad 16-Bit,1 GSPS, TxDAC+ Digital-to-Analog Converter
• Manufacturer: AD [Analog Devices]

Preliminary Technical Data
SERIAL PERIPHERAL INTERFACE
The serial port is a flexible, synchronous serial communications
port allowing easy interface to many industry-standard micro-
controllers and microprocessors. The serial I/O is compatible
with most synchronous transfer formats, including both the
Motorola SPI and Intel
read/write access to all registers that configure the AD9148.
Single- or multiple-byte transfers are supported, as well as MSB-
first or LSB-first transfer formats. The serial interface ports can
be configured as a single pin I/O (SDIO) or two unidirectional
pins for input/output (SDIO/SDO).
GENERAL OPERATION OF THE SERIAL INTERFACE
There are two phases to a communication cycle with the AD9148.
Phase 1 is the instruction cycle (the writing of an instruction
byte into the device), coincident with the first eight SCLK rising
edges. The instruction byte provides the serial port controller
with information regarding the data transfer cycle, Phase 2 of
the communication cycle. The Phase 1 instruction byte defines
whether the upcoming data transfer is a read or write and the
starting register address for the first byte of the data transfer.
The first eight SCLK rising edges of each communication cycle
are used to write the instruction byte into the device.
A logic high on the CSB pin followed by a logic low resets the
SPI port timing to the initial state of the instruction cycle. From
this state, the next eight rising SCLK edges represent the instruction
bits of the current I/O operation, regardless of the state of the
internal registers or the other signal levels at the inputs to the
SPI port. If the SPI port is in an instruction cycle or a data
transfer cycle, none of the present data is written.
The remaining SCLK edges are for Phase 2 of the communication
cycle. Phase 2 is the actual data transfer between the device and
the system controller. Phase 2 of the communication cycle is a
transfer of one or more data bytes. Registers change immediately
upon writing to the last bit of each transfer byte.
SCLK
®
SDIO
SDO
CSB
SSR protocols. The interface allows
Figure 40. SPI Por
G1
H1
G2
H2
PORT
SPI
t
Rev. PrA | Page 21 of 73
DATA FORMAT
The instruction byte contains the information shown in Table 11.
Table 11. SPI Instruction Byte
I7 (MSB)
R/W
R/ W , Bit 7 of the instruction byte, determines whether a read or
a write data transfer occurs after the instruction byte write.
Logic high indicates a read operation, and Logic 0 indicates a
write operation.
A6 through A0—Bit 6 through Bit 0 of the instruction byte
determine the register that is accessed during the data transfer
portion of the communication cycle. For multibyte transfers, this
address is the starting byte address. The remaining register
addresses are generated by the device based on the LSB-first bit
(Register 0x00, Bit 6).
SPI PIN DESCRIPTIONS
Serial Clock (SCLK)
The serial clock pin synchronizes data to and from the device
and runs the internal state machines. The maximum frequency
of SCLK is 40 MHz. All data input is registered on the rising
edge of SCLK. All data is driven out on the falling edge of SCLK.
Chip Select (CSB)
Active low input starts and gates a communication cycle. It
allows more than one device to be used on the same serial
communications lines. The SDO and SDIO pins go to a high
impedance state when this input is high. Chip select should stay
low during the entire communication cycle.
Serial Data I/O (SDIO)
Data is always written into the device on this pin. However, this
pin can be used as a bidirectional data line. The configuration
of this pin is controlled by Register 0x00, Bit 7. The default is
Logic 0, configuring the SDIO pin as unidirectional.
Serial Data Out (SDO)
Data is read from this pin for protocols that use separate lines
for transmitting and receiving data. In the case where the device
operates in a single bidirectional I/O mode, this pin does not
output data and is set to a high impedance state.
I6
A6
I5
A5
I4
A4
I3
A3
I2
A2
I1
A1
AD9148
I0 (LSB)
A0