AD9974BBCZ datasheet(40/52 Pages) AD

40 / 52 page

AD9974

Rev. A | Page 40 of 52

LAYOUT OF INTERNAL REGISTERS

The AD9974 address space is divided into two register areas, as

shown in Figure 54. In the first area, Address 0x00 to Address 0x72

contain the registers for the AFE, miscellaneous functions, VD/HD

parameters, I/O control, mode control, timing core, and update

control functions. The second area of the address space, beginning

at Address 0x800, consists of the registers for the H-pattern groups

and fields. This is a configurable set of register spaces; the user

can decide how many H-patterns and fields are used in a particular

design. The AD9974 supports the use of up to 32 H-patterns.

The starting address for the H-pattern groups is always 0x800.

The starting address for the field registers is determined by the

number of H-pattern groups. Each H-pattern group and field

occupies 16 register addresses.

The starting address for the field registers is based on the

number of H-pattern groups and is equal to 0x800 plus the

number of H-pattern groups times 16.

It is important to note that the H-pattern and field registers

must always occupy a continuous block of addresses.

Figure 55 shows an example when three H-pattern groups and

two fields are used. The starting address for the H-pattern groups

is always 0x800. Because HPATNUM is 3, the H-pattern groups

occupy 48 address locations (that is, 16 registers × 3 H-pattern

groups). The starting address of the field registers for this example

is 0x830 (that is, 0x800 + 48 (decimal)). Note that the decimal value

must be converted to a hex number before adding it to 0x800.

The AD9974 address space contains many unused addresses. Any

undefined addresses between Address 0x00 and Address 0x7FF

should not be written to; otherwise, the AD9974 may operate

incorrectly. Continuous register writes should be performed

carefully so that undefined registers are not written to.

FIXED REGISTER AREA

AFE REGISTERS

MISCELLANEOUS FUNCTION REGISTERS

VD/HD REGISTERS

I/O REGISTERS

MODE CONTROL REGISTERS

TIMING CORE REGISTERS

TEST REGISTERS

UPDATE CONTROL REGISTERS

INVALID—DO NOT ACCESS

CONFIGURABLE REGISTER AREA

H-PATTERN GROUPS

FIELDS

ADDR 0x000

ADDR 0x7FF

HPAT START 0x800

FIELD START

MAX 0xFFF

NOTES

1. THE H-PATTERN AND FIELD REGISTERS MUST ALWAYS OCCUPY A CONTINUOUS BLOCK OF ADDRESSES.

Figure 54. Layout of AD9974 Registers

2 FIELDS

(16 × 2 = 32 REGISTERS)

3 H-PATTERN GROUPS

(16 × 3 = 48 REGISTERS)

UNUSED MEMORY

ADDR 0x800

ADDR 0x830

ADDR 0x850

MAX 0xFFF

Figure 55. Example Register Configuration

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