Disabling The Parity Circuits - Zenith Z-100 Reference Manual

Page 6.12
System Memory
For example, the value 3F3F:5B11 would represent memory address 44F01
hexadecimal (282369 dedmal), since 3F3F shifted left equals 3F3FO (259056 deci-
mal) plus 5B11 (23313 decimal) equals 44F01H.
Since the least-significant digit of the segment is always 0, it should be apparent
that more than one combination of segment and offset can point to the same
memory address. For instance, the address arrived at in our previous example
could also be defined by:
The highest and lowest usable segment value are determined by the memory
address in question. For our example address, the lowest usable segment value
would be 34F1H, since anything lower would result in an offset greater than FFFFH.
The highest usable segment value would be 44FOH.

Disabling the Parity Circuits

To disable the parity check and/or generation circuitry, send a value between
1 and 3 to the parity check and generation disable port at 100H. The disable
port responds to values defined in Table 6.3.
Table 6.3. Parity Disable Output Port Values
VALUE RE S ULT
0 Reset to normal (no disable)
1 Disable parity check
Disable parity generation
2
Disable both parity generation and checking
3
3FOO:5F01