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AD9920A

Rev. B | Page 66 of 112

Single-Field Toggles

Single-field toggles occur in the next field only. There can be up to

four toggles in the field. The mode is set with GP_PROTOCOL

equal to 1, and the toggles are triggered in the next field by

writing to the MANUAL_TRIG register (Register 0x70, Bits[13:6]).

In this mode, the field toggle settings must be set to a value of 1.

Two consecutive fields do not have activity. If toggles are required

to repeat in the next field, the MANUAL_TRIG register can be

written to in consecutive fields.

Preparation

The GP toggle positions can be programmed any time prior to

use. For example,

0x7C

← 0x000A001

0x7D

← 0x0002000

0x7E

← 0x000000F

0x7F

← 0x00C4002

0x80

← 0x0004000

0x81

← 0x00000B3

Details

A) Field 0:

0x70

← 0x0000040

0x73

← 0x0000001

B) Field 1:

0x73

← 0x0000000

GP1_PROTOCOL 0

GPO1

NOTES

1. THE FIELD TOGGLE POSITION MUST BE SET TO 1 WHEN

GP PROTOCOL IS 1.

CAUTION! THE GP_PROTOCOL MUST BE RESET BEFORE

USING AGAIN.

Figure 84. Single-Field Toggles Using GP_PROTOCOL = 1

Scheduled Toggles

Scheduled toggles are programmed to occur during upcoming

fields. For example, there can be one toggle in Field 1, two

toggles in Field 3, and a last toggle in Field 4. The mode is set

with GP_PROTOCOL = 5 or GP_PROTOCOL = 6. Mode 5

tells the GPO to obey the primary field counter, and Mode 6

tells the GPO to obey the secondary field counter.

Note that for GP_PROTOCOL = 5 or GP_PROTOCOL = 6, at

least one toggle must be programmed in Field 1 for the AD9920A

to output the proper pattern on the GPO pins. If no toggle is

programmed in Field 1, all subsequent toggle positions are

ignored when GP_PROTOCOL = 5 or GP_PROTOCOL = 6.

This restriction applies only to GP_PROTOCOL = 5 or

GP_PROTOCOL = 6.

Preparation

The GP toggle positions can be programmed any time prior to

use. For example,

0x7C

← 0x00C4001

0x7D

← 0x0004000

0x7E

← 0x00000B3

Details

A) Field 0:

0x70

← 0x0000008

0x73

← 0x0000006

GP1_PROTOCOL 0

SECONDARY

COUNT

GPO1

CAUTION! THE PRIMARY COUNTER REGULATES THE SUBCK

AND VSG ACTIVITY. LINK A GPO TO THE PRIMARY COUNTER

ONLY IF SUBCK AND VSG ACTIVITY WILL OCCUR DURING

EXPOSURE/READ.

(IDLE)

Figure 85. Scheduled Toggles Using GP_PROTOCOL = 6

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