AD9520-5SLASHPCBZ datasheet(54/80 Pages) AD

54 / 80 page

AD9520-5

Rev. 0 | Page 54 of 80

If the AD9520 register map were continuous from Address 0x000

to Address 0x232, only one register section definition group

would consist of a starting address of 0x000 and a length of

563 bytes. However, this is not the case. The AD9520 register

map is noncontiguous, and the EEPROM is only 512 bytes long.

Therefore, the register section definition group tells the EEPROM

controller how the AD9520 register map is segmented.

There are three operational codes: IO_UPDATE, end-of-data,

and pseudo-end-of-data. It is important that the EEPROM buffer

segment always have either an end-of-data or a pseudo-end-of-data

operational code and that an IO_UPDATE operation code appear

at least once before the end-of-data op code.

The register section definition group is used to define a continuous

The first byte defines how many continuous register bytes are in

this group. If the user puts 0x000 in the first byte, it means there

is only one byte in this group. If the user puts 0x001, it means

there are two bytes in this group. The maximum number of

registers in one group is 128.

The next two bytes are the low byte and high byte of the

memory address (16-bit) of the first register in this group.

IO_UPDATE (Operational Code 0x80)

The EEPROM controller uses this operational code to generate

an IO_UPDATE signal to update the active control register

bank from the buffer register bank during the download process.

At a minimum, there should be at least one IO_UPDATE

operational code after the end of the final register section definition

group. This is needed is so that at least one IO_UPDATE occurs

after all of the AD9520 registers are loaded when the EEPROM

is read. If this operational code is absent during a write to the

EEPROM, the register values loaded from the EEPROM are not

transferred to the active register space, and these values do not

take effect after they are loaded from the EEPROM to the AD9520.

End-of-Data (Operational Code 0xFF)

The EEPROM controller uses this operational code to terminate

the data transfer process between EEPROM and the control

appearing in the EEPROM buffer segment should be either this

operational code or the pseudo-end-of-data operational code.

Pseudo-End-of-Data (Operational Code 0xFE)

The AD9520 EEPROM buffer segment has 23 bytes that can

contain up to seven register section definition groups. If users

want to define more than seven register section definition

groups, the pseudo-end-of-data operational code can be used.

During the upload process, when the EEPROM controller

receives the pseudo-end-of-data operational code, it halts the

data transfer process, clears the REG2EEPROM bit, and enables

the AD9520 serial port. Users can then program the EEPROM

buffer segment again and reinitiate the data transfer process by

setting the REG2EEPROM bit (0xB03) to 1 and the IO_UPDATE

the EEPROM starting from the EEPROM address held from the

last writing.

This sequence enables more discrete instructions to be written

to the EEPROM than would otherwise be possible due to the

limited size of the EEPROM buffer segment. It also permits the

user to write to the same register multiple times with a different

value each time.

Table 42. Example of EEPROM Buffer Segment

Reg Addr (Hex)

Bit 7 (MSB)

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0 (LSB)

Start EEPROM Buffer Segment

0xA00

Number of bytes [6:0] of the first group of registers

0xA01

Address [15:8] of the first group of registers

0xA02

Address [7:0] of the first group of registers

0xA03

Number of bytes [6:0] of the second group of registers

0xA04

Address [15:8] of the second group of registers

0xA05

Address [7:0] of the second group of registers

0xA06

Number of bytes [6:0] of the third group of registers

0xA07

Address [15:8] of the third group of registers

0xA08

Address [7:0] of the third group of registers

0xA09

IO_UPDATE operational code (0x80)

0xA0A

End-of-data operational code (0xFF)

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