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AD9558

Data Sheet

Rev. A | Page 46 of 104

EEPROM Conditional Processing

The condition tag board is a table maintained by the EEPROM

controller. When the controller encounters a condition instruc-

tion, it decodes the B1 through CF instructions as Condition = 1

through Condition = 8, respectively, and tags that particular

condition in the condition tag board. However, the B0 condition

instruction decodes as the null condition, for which the controller

clears the condition tag board; and subsequent download

instructions execute unconditionally (until the controller

encounters a new condition instruction).

The condition instructions allow conditional execution of

EEPROM instructions during a download sequence. During

an upload sequence, however, they are stored as is and have

no effect on the upload process.

Note that, during EEPROM downloads, the condition instructions

themselves and the end instruction always execute unconditionally.

Conditional processing makes use of two elements: the condition

(from Condition 1 to Condition 8) and the condition tag board.

The relationships among the condition, the condition tag board,

and the EEPROM controller appear schematically in Figure 45.

During download, the EEPROM controller executes or skips

instructions depending on the value of the condition and the

contents of the condition tag board. Note, however, that the

condition instructions and the end instruction always execute

unconditionally during download. If condition = 0, then all

instructions during download execute unconditionally. If

Condition ≠ 0 and there are any tagged conditions in the condition

tag board, then the controller executes instructions only if the

condition is tagged. If the condition is not tagged, then the

controller skips instructions until it encounters a condition

instruction that decodes as a tagged condition. Note that the

condition tag board allows for multiple conditions to be tagged

at any given moment. This conditional processing mechanism

enables the user to have one download instruction sequence

with many possible outcomes depending on the value of the

condition and the order in which the controller encounters

condition instructions.

The condition is a 4-bit value with 16 possibilities. Condition = 0

is the null condition. When the null condition is in effect, the

EEPROM controller executes all instructions unconditionally.

Condition 9 through Condition 15 are not accessible using the

M pins. The remaining eight possibilities (that is, Condition = 1

through Condition = 8) modify the EEPROM controller’s

handling of a download sequence. The condition originates

from one of two sources (see Figure 45), as follows:

•

FncInit, Bits[3:0], which is the state of the M2 and M3

multifunction pins at power-up (see Table 22)

•

If Register 0x0E01, Bits[3:0] ≠ 0, then the condition is the value

that is stored in Register 0x0E01, Bits[3:0]; otherwise, the condition

is FncInit, Bits[3:0]. Note that a nonzero condition that is present

in Register 0x0E01, Bits[3:0] takes precedence over FncInit,

Bits[3:0].

EXAMPLE

CONDITION 3 AND

CONDITION 13

ARE TAGGED

EEPROM

EEPROM CONTROLLER

UPLOAD

PROCEDURE

CONDITION

HANDLER

DOWNLOAD

PROCEDURE

CONDITION

TAG BOARD

IF B1 ≤ INSTRUCTION ≤ CF,

THEN TAG DECODED CONDITION

EXECUTE/SKIP

INSTRUCTION(S)

SCRATCH

PAD

COND ITION

CONDITION = 0E01

, BITS[3:0]

ELSE

CONDITION = FncInit, BITS[3:0]

ENDIF

M3 AND M2 PINS

(3-LEVEL LOGIC)

IF INSTRUCTION = B0,

THEN CLEAR ALL TAGS

FncInit, BITS[3:0]

0x0E01, BITS[3:0]

STORE CONDITION

INSTRUCTIONS AS

THEY ARE READ FROM

THE SCRATCH PAD.

WATCH FOR

OCCURRENCE OF

CONDITION

INSTRUCTIONS

DURING

DOWNLOAD.

IF {NO TAGS} OR {CONDITION = 0}

EXECUTE INSTRUCTIONS

ELSE

IF {CONDITION IS TAGGED}

EXECUTE INSTRUCTIONS

ELSE

SKIP INSTRUCTIONS

ENDIF

IF {0E01, BITS[3:0] ≠ 0}

Figure 45. EEPROM Conditional Processing

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