I am not clear on the usage of the registers 0x1D to 0x20 named "User Pattern
3" and "User Pattern 4". They are not mentioned at all in the technical note
AN-877, where it is described only the usage of the registers "User Pattern 1"
and "User Pattern 2".
I've observed that in the user test mode also these two registers are used, but
in which way?
This is not described in the technical documentation.
The AD9613 has a slightly different implementation with regards to the User
Test patterns than what is presented in AN-877.
In the AD9613, when bit 7 of reg 0x0D is set to ‘1’ then the patterns in
registers 0x19 through 0x20 (user patterns 1, 2, 3, 4) are placed on the output
for one clock cycle each and then the output goes to ‘0’. If bit 7 of reg 0x0D
is set to ‘0’ then the patterns in registers 0x19 through 0x20 are repeated
continuously on the output (1, 2, 3, 4, 1, 2, 3, 4,….). I would like to point
out that the register has more space than needed to accommodate the 12 bit
outputs of the AD9613 so the 4 LSBs in each user pattern will be truncated.