ACT apricot - Address Allocation

EXPANSION SLOTS
External Terminate for DMA Channel 2.
Input connected to the External Terminate
line (EXT2) of the 8089 lOP via an inverter. A
logic
low on EXT2 requests the lOP to
terminate the current DMA transfer
operation on DMA Channel 2.
Interrupt Request (Priority 2). Input line
connected to the Interrupt Request 2 input of
the Programmable Interrupt Controller (PIC)
via an inverter. The interrupt type number
supplied to the 8086 processor on
acknowledgement of the interrupt request is
52H. (The
interrupt type number acts as a
pointer to the interrupt service routine.)
Interrupt Request (Priority 3). Input line
connected to the Interrupt Request 3 input of
the PIC via an inverter. The interrupt type
number supplied to the 8086 processor on
acknowledgement of the interrupt request is
53H. (The interrupt type number act as a
pointer to the interrupt service routine.)
Non-Maskable Interrupt. Input connected to
the NMI input of the 8086_processor via an
inverter. A logic high to low transition on
NMI generates the predefined interrupt type
number2 internally within the 8086, which
acts as a pointer to an interrupt service
routine.
Address Allocation
The available address locations in the system memory
space and input/output space allocated to the Expansion
Slots are detailed below. 8-bit devices connected to the
lower half of the data bus must be located on even address
boundaries and 8-bit devices connected to the upper half, on
odd address boundaries.
System memory: 40000H to EFFFFH.
System I/O: 80H to IFFH excluding F8H to FFH.