Datasheet

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
VD
1
REGISTER WRITE
AB
GP1_PROTOCOL 0 1 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.
06878-084
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
VD 1 2
REGISTER WRITE
A
GP1_PROTOCOL
0
SECONDARY
COUNT
01
6
20
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)
06878-085
Figure 85. Scheduled Toggles Using GP_PROTOCOL = 6