How long do you have to wait before writing to $2140-$2143?

This is an archive of a topic from NESdev BBS, taken in mid-October 2019 before a server upgrade.
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How long do you have to wait before writing to $2140-$2143?
by psycopathicteen on 2019-10-06 (#243047)
After you sent the spc700 data, how long do you have to wait before you can safetly write over $2140-$2143.

Also, what values do $2140-$2143 show after boot up when read from the CPU?
Re: How long do you have to wait before writing to $2140-$21
by calima on 2019-10-07 (#243060)
You wait for your sound driver to acknowledge your writes, however long it takes.