External Use Of Ta_ And Tea - Digi NS7520B-1-C36 Hardware Reference Manual

Workaround
Use the software workaround for the mode you are using:
Interrupt mode:
For all but the first character, check the TXEMPTY bit (D00 in the Serial
Status Register A).
–
–
DMA mode:
You should not have a problem with this issue when working in DMA mode.

External use of TA_ and TEA_

Note these issues for TA_ and TEA_:
TEA_: Externally generated TEA_ burst cycles can cause failures.
TA_: External TA_ can be used only in single cycle mode, to terminate chip
selects with 8, 16, and 32 bus widths.
Workaround
The TA_ signal in the NS7520 must be synchronized with BCLK, and last for one BCLK.
The internal TA synchronizer settings must be as shown:
Chip Select Option Register B: SYNC — 1 stage (01)
System Control register — BSYNC: 1 stage (00)
Both TA_ and TEA_ should have external 820 ohm pullups.
The external device never drives TEA_.
Note:
If the TXEMPTY bit is not set, write the next character within 1 character
time.
If the TXEMPTY bit is set, wait 1 character time plus 1 bit time before
writing the next character.
w w w . d i g i e m b e d d e d . c o m
N S 7 5 2 0 E r r a t a
3 1 3