Datasheet

Data Sheet AD9257
Rev. A | Page 31 of 40
MEMORY MAP REGISTER TABLE
The AD9257 uses a 3-wire interface and 16-bit addressing and,
therefore, Bit 0 and Bit 7 in Register 0x00 are set to 0, and Bit 3
and Bit 4 are set to 1. When Register 0x00, Bit 5 is set high, the
SPI enters a soft reset, where all of the user registers revert to
their default values and Bit 2 is automatically cleared.
Table 17. Memory Map Register Table
Reg.
Addr.
(Hex) Register Name
Bit 7
(MSB) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 (LSB)
Default
Value
(Hex) Comments
Chip Configuration Registers
0x00 SPI port
configuration
0 = SDO
active
LSB first Soft reset 1 =
16-bit
address
1 = 16-bit
address
Soft reset LSB first 0 = SDO
active
0x18 The nibbles
are mirrored
so that LSB
or MSB first
mode registers
correctly. The
default for the
ADCs is 16-bit
mode.
0x01 Chip ID (global) 8-bit chip ID, Bits[7:0]
AD9257 0x92 = octal 14-bit, 40 MSPS/65 MSPS serial LVDS
Read
only
0x92
Unique chip ID
that is used to
differentiate
devices; read
only.
0x02 Chip grade
(global)
Open Speed grade ID, Bits[6:4]
001 = 40 MSPS
011 = 65 MSPS
Open Open Open Open Read
only
Unique
speed grade
ID used to
differentiate
graded
devices.
Read only.
Device Index and Transfer Registers
0x04 Device Index 2 Open Open Open Open Data
Channel H
Data
Channel G
Data
Channel F
Data
Channel E
0xF Bits are set
to determine
which device
on chip
receives the
next write
command.
The default
is all devices
on chip.
0x05 Device Index 1 Open Open Clock
Channel
DCO
Clock
Channe
l FCO
Data
Channel D
Data
Channel C
Data
Channel B
Data
Channel A
0x3F Bits are set
to determine
which device
on chip
receives the
next write
command.
The default
is all devices
on chip.
0xFF Transfer Open Open Open Open Open Open Open Initiate
override
0x00 Set resolution/
sample rate
override.
Global ADC Functions
0x08 Power modes
(global)
Open Open External
power-
down pin
function
0 = full
power-
down
1 =
standby
Open Open Open Internal power-down
mode
00 = chip run
01 = full power-down
10 = standby
11 = reset
0x00 Determines
various
generic modes
of chip
operation.
0x09 Clock (global) Open Open Open Open Open Open Open Duty cycle
stabilize
0 = off
1 = on
0x01 Turns duty
cycle stabilizer
on or off.