Serial Port Error In 7-Bit Mode; Sdram 256 Mb Mask Failure; Erroneous Timeouts When Loading Timer - Digi NS7520B-1-C36 Hardware Reference Manual

Serial port error in 7-bit mode

The NS7520's serial ports do not function correctly when configured in the 7-bit
mode. The 7-bit transmitter will transmit 8-bit data, and the data in the receive
buffer will be incorrect. The other modes — 8-bit, 6-bit, and 5-bit — all function
correctly.
Workaround
None. Use the 8-bit, 6-bit, or 5-bit modes only.

SDRAM 256 MB mask failure

The NS7520 chip select does not generate the required precharge commands if a
value larger than 128 MB is written in the Chip Select Option register mask word. In
particular, if the SDRAM is located at 0–256M and one read is done at address
another read is done at address
address 0.
Workaround
Mask size

Erroneous timeouts when loading timer

There can be two erroneous timeouts when the timer is first loaded.
Workaround
In most cases, no workaround is required because the error averages out over many
readings. The problem can become critical if you set the timer to a large value, such
as four hours. A workaround for this situation is to program the timer to timeout
twice, with a small value such as 4μ, then load the larger value.
0x0
(256 MB) should not be used.
0xF0000
, there is no precharge for the read at
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
and
0x400
3 0 9