AD6655 Analog Devices, AD6655 Datasheet - Page 50

• Manufacturer Part Number: AD6655
• Description: IF Diversity Receiver
• Manufacturer: Analog Devices

AD6655
MEMORY MAP
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 0x18); and the digital
feature control registers (Address 0x100 to Address 0x123).
The memory map register table (see Table 29) documents 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
VREF select register, has a hexadecimal default value of 0xC0. This
means that Bit 7 = 1, Bit 6 = 1, and the remaining bits are 0s. This
setting is the default reference selection setting. The default value
uses a 2.0 V p-p reference. For more information on this function
and others, see Application Note AN-877, Interfacing to High Speed
ADCs via SPI. This document details the functions controlled by
Register 0x00 to Register 0xFF. The remaining registers, from
Register 0x100 to Register 0x123, are documented in the Memory
Map Register Description section.
Open Locations
All address and bit locations that are not included in Table 29
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.
Default Values
After the AD6655 is reset, critical registers are loaded with
default values. The default values for the registers are given in
the memory map register table, Table 29.
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Logic Levels
An explanation of logic level terminology follows:
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Transfer Register Map
Address 0x08 to Address 0x18 and Address 0x11E to
Address 0x123 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 autoclears.
Channel-Specific Registers
Some channel setup functions, such as the signal monitor
thresholds, can be programmed differently for each channel.
In these cases, channel address locations are internally duplicated
for each channel. These registers and bits are designated in Table 29
as local. These local registers and bits can be accessed by setting
the appropriate Channel A or Channel B bits in Register 0x05. If
both bits are set, the subsequent write affects the registers of both
channels. In a read cycle, only Channel A or Channel 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.
Registers and bits designated as global in Table 29 affect the entire
part or the channel features where 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. ”