86:Ports:06

Synopsis

Port Number: 06h

Function: Upper Memory Bank Port

This port controls which memory bank is accessible in the 8000-BFFFh range. See Memory Mapping for the interpretation of the banks & pages.

Read Values

• Bit 0-7: Reads last value written.

Write Values

• Bit 0-5: Page select (external address bits 14-19).
• Bit 6-7: Bank select.

Comments

• This port is set to 41h when the OS passes control to a program. Its value at program exit is ignored.