AD9644 Analog Devices, AD9644 Datasheet - Page 33
Manufacturer Part Number
14-Bit, 80 MSPS/155 MSPS, 1.8V Dual, Serial Output A/D Converter
Specifications of AD9644
Analog Input Type
1.75 V p-p
READING THE MEMORY MAP REGISTER TABLE
Each row in the memory map register table has eight bit locations.
The memory map is roughly divided into four sections: the chip
configuration registers (Address 0x00 to Address 0x02); the
channel index and transfer registers (Address 0x05 and
Address 0xFF); the ADC functions registers, including setup,
control, and test (Address 0x08 to Address 0x3A); and the
JESD204A configuration registers (Address 0x5E to Address 0x79).
The memory map register table (see Table 17) lists the default
hexadecimal value for each hexadecimal address shown. The
column with the heading Bit 7 (MSB) is the start of the default
hexadecimal value given. For example, Address 0x18, the input
span select register, has a hexadecimal default value of 0x00. This
means that Bit 0 through Bit 4 = 0, and the remaining bits are 0s.
This setting is the default reference selection setting. The default
value uses a 1.75 V p-p reference. For more information on this
function and others, see the
to High Speed ADCs via SPI. This application note details the
functions con-trolled by Register 0x00 to Register 0xFF.
All address and bit locations that are not included in Table 17
are not currently supported for this device. Unused bits of a
valid address location should be written with 0s. Writing to these
locations is required only when part of an address location is
open (for example, Address 0x18). If the entire address location
is open (for example, Address 0x13), this address location should
not be written.
After the AD9644 is reset, critical registers are loaded with
default values. The default values for the registers are given in
the memory map register table, Table 17.
Application Note, Interfacing
Rev. C | Page 33 of 44
An explanation of logic level terminology follows:
Transfer Register Map
Address 0x08 through Address 0x79 are shadowed. Writes to
these addresses do not affect part operation until a transfer
command is issued by writing 0x01 to Address 0xFF, setting the
transfer bit. This allows these registers to be updated internally
and simultaneously when the transfer bit is set. The internal
update takes place when the transfer bit is set, and the bit
Some channel setup functions, such as the channel output
mode, can be programmed differently for each ADC or link
channel. In these cases, channel address locations are internally
duplicated for each channel. These registers and bits are
designated in Table 17 as local. These local registers and bits can
be accessed by setting the appropriate Channel A/Link A or
Channel B/Link B bits in Register 0x05.
If both bits are set in register 0x05, the subsequent write affects
the registers of both channels/links. In a SPI read cycle, only
Channel A/Link A or Channel B/Link B should be set to read
one of the two registers. If both bits are set during an SPI read
cycle, the part returns the value for Channel A/Link A. Registers
and bits designated as global in Table 17 affect the entire part or the
channel features for which independent settings are not allowed
between channels. The settings in Register 0x05 do not affect
the global registers and bits.
“Bit is set” is synonymous with “bit is set to Logic 1” or
“writing Logic 1 for the bit. ”
“Clear a bit” is synonymous with “bit is set to Logic 0” or
“writing Logic 0 for the bit. ”