Toshiba T1200 - Appendix E: EMC (EXPANDED MEMORY CONTROLLER)G.A.; E.1 GENERAL

APPBRDIX B
BIle (BXPARDBD MBMORY CORftOLLBR)G.A.
E.l GBRBRAL
This gate array is compatible with Lotus/Intel/Microsoft
Expanded Memory Specification, and is composed of 100 pins
altogether.
Within the memory address space C4000H-EFFFFH, the
consecutive 64-kbyte space is reserved as the EM window.
Each EM unit can control up to 2 Mbytes (128 pages), and as
one system can control up to four EM units, the whole system
can have maximum 8-Mbyte space.
All of this is possible in theory, but in fact, as there is
a limit in the real installation, the maximum 384-kbyte
address space is provided as its standard mode.
I/O ports used for the EM unit are 2X8H-2XFH, and different
I/O por is assigned for each unit (X can be any of the
numbers - 0, 1, 5, 6, A, B, E).
Through the Page Register in the EM assigned to this I/O
port, 64-kbyte window can be assigned on the Expansion
Memory.
E - 1