AD9551/PCBZ Analog Devices Inc, AD9551/PCBZ Datasheet - Page 26

• Manufacturer Part Number: AD9551/PCBZ
• Description: BOARD EVAL FOR AD9951
• Manufacturer: Analog Devices Inc

Specifications of AD9551/PCBZ

• Main Purpose: Timing, Clock Generator
• Embedded: No
• Utilized Ic / Part: AD9551
• Primary Attributes: 2 Inputs, 2 Outputs, VCO
• Secondary Attributes: Graphical User Interface, USB Interface
• Silicon Manufacturer: Analog Devices
• Application Sub Type: Clock Generator
• Kit Application Type: Clock & Timing
• Silicon Core Number: AD9551
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD9551
SERIAL CONTROL PORT
The AD9551 serial control port is a flexible, synchronous, serial
communications port that allows an easy interface to many
industry-standard microcontrollers and microprocessors. Single
or multiple byte transfers are supported, as well as MSB first or
LSB first transfer formats. The AD9551 serial control port is
configured for a single bidirectional I/O pin (SDIO only).
The serial control port has two types of registers: read-only and
buffered. Read-only registers are nonbuffered and ignore write
commands. All writable registers are buffered (also referred to
as mirrored) and require an I/O update to transfer the new values
from a temporary buffer on the chip to the actual register. To
invoke an I/O update, write a 1 to the I/O update bit found in
Register 0x05[0]. Because any number of bytes of data can be
changed before issuing an update command, the update simul-
taneously enables all register changes occurring since any
previous update.
SERIAL CONTROL PORT PIN DESCRIPTIONS
SCLK (serial data clock) is the serial shift clock. This pin is an
input. SCLK is used to synchronize serial control port reads and
writes. Write data bits are registered on the rising edge of this
clock, and read data bits are registered on the falling edge. This
pin is internally pulled down by a 30 kΩ resistor to ground.
SDIO (digital serial data input/output) is a dual-purpose pin
that acts as input only or as an input/output. The AD9551
defaults to bidirectional pins for I/O.
CS (chip select bar) is an active low control that gates the read and
write cycles. When CS is high, SDIO is in a high impedance state.
This pin is internally pulled up by a 100 kΩ resistor to 3.3 V and
should not be left floating. See the
Port
OPERATION OF THE SERIAL CONTROL PORT
Framing a Communication Cycle with CS
The CS line gates the communication cycle (a write or a read oper-
ation). CS must be brought low to initiate a communication cycle.
The CS stall high function is supported in modes where three
or fewer bytes of data (plus instruction data) are transferred.
Bits[W1:W0] must be set to 00, 01, or 10 (see
modes,
allowing time for the system controller to process the next byte. CS
can go high on byte boundaries only and can go high during either
part (instruction or data) of the transfer. During this period, the
section on the use of the
CS may temporarily return high on any byte boundary,
SCLK
SDIO
Figure 24. Serial Control Port
CS
14
15
13
CS pin in a communication cycle.
AD9551
CONTROL
Operation of the Serial Control
SERIAL
PORT
Table 19
). In these
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serial control port state machine enters a wait state until all data
has been sent. If the system controller decides to abort before
the complete transfer of all the data, the state machine must be reset
either by completing the remaining transfer or by returning the CS
line low for at least one complete SCLK cycle (but fewer than
eight SCLK cycles). A rising edge on the CS pin on a nonbyte
boundary terminates the serial transfer and flushes the buffer.
Table 19. Byte Transfer Count
In the streaming mode (Bits[W1:W0] = 11), any number of data
bytes can be transferred in a continuous stream. The register
address is automatically incremented or decremented (see the
MSB/LSB First Transfers section). CS must be raised at the end
of the last byte to be transferred, thereby ending the stream mode.
Communication Cycle—Instruction Plus Data
There are two parts to a communication cycle with the AD9551.
The first part writes a 16-bit instruction word into the AD9551,
coincident with the first 16 SCLK rising edges. The instruction
word provides the AD9551 serial control port with information
regarding the data transfer, which is the second part of the
communication cycle. The instruction word defines whether
the upcoming data transfer is a read or a write, the number of
bytes in the data transfer, and the starting register address for
the first byte of the data transfer.
Write
If the instruction word is for a write operation (Bit I15 = 0), the
second part is the transfer of data into the serial control port
buffer of the AD9551. The length of the transfer (1, 2, or 3 bytes;
or streaming mode) is indicated by two bits (Bits[W1:W0])
in the instruction byte. The length of the transfer indicated by
(Bits[W1:W0]) does not include the 2-byte instruction. CS can
be raised after each sequence of eight bits to stall the bus (except
after the last byte, where it ends the cycle). When the bus is stalled,
the serial transfer resumes when CS is lowered. Stalling on nonbyte
boundaries resets the serial control port.
Read
If the instruction word is for a read operation (Bit I15 = 1), the
next N × 8 SCLK cycles clock out the data from the address
specified in the instruction word, where N is 1, 2, 3, or 4, as
determined by Bits[W1:W0]. In this case, 4 is used for streaming
mode, where four or more words are transferred per read. The
data read back is valid on the falling edge of SCLK.
The default mode of the AD9551 serial control port is bidirec-
tional mode, and the data read back appears on the SDIO pin.
W1
0
0
1
1
W0
0
1
0
1
Bytes to Transfer
(Excluding the 2-Byte Instruction)
1
2
3
Streaming mode