Tandy 1000
Technical Reference Manual
System Configuration Port
I/O
Address:
OOAO
Data
Bit Function
Selects 1 Of 8 - 128K
01 MEMCONFIG 1 Memory Pages Where
02
MEMCONFIG 2 Video/System
Ram
Memory
03
MEMCONFIG 3
To
Be
Located. See
Memory Map For Details.
Register Located Main Logic.
04
Reserved
05
Reserved
06
Reserved
07
NMIEN Enables NMI Input
To
CPU 0 = Mask 1 = Enable
Register Located Main Logic.
ROM
System
ROM
Size:
16K x 8 (128K)
32K x 8 (256K) optional
Quantity: 1 or
2,
socketed
Address Range - ROM:
FOOOO
To
FFFFF
Two 32K address segments are decoded
in
hardware.
There will always be one system
ROM
located at the boot segment
F8000 -
FFFFF.
The second system
ROM
will be limited to the
second address segment
FOOOO
- F7FFF.
No error detection capability.
RAM
RAM
address range: 00000
to
B8000
RAM memory used by the CPU must be continuous beginning
at
00000.
Address selection granularity - 64K.
Video memory access
at
B8000/COOOO.
Presence (quantity)
of
RAM
in
addition to video/system
RAM
determined
by initialization routing.
Video system
RAM
memory address select defined by "MEMCONFIG"
register at
OOAO.
On power-up or reset, address defaults
to
B8000.
No memory error detection capability.
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