Block-Select Memory Expansion; Rom Addressing; I/O Port Address - Advanced Micro Computers Am96/4116A User Manual

TABLE 3-1. I/O PORT ADDRESS
.-
I/O PORT
I/O INPUT (READ)
OUTPUT (WRITE)
I/O ADDRESS BITS ADDRESS DEVICE
FUNCTION FUNCTION
FED C B A 9 8 7 6 543 2 1 0
--
1 1 - - - - - - - - 000 0 0 0
FFCO
Single Step Write FFCO
1 1 - - - - - - - - 0 0 1 000
FFC8 8259A Read ISR, IRR, or
Write ICW1 and OCW2,3
Interrupt
Polled Status
1 1 - - - - - - - - 0 0 1 010
FFCA Controller Read IMR
Write ICW2. 4, and OCW1
1 1 - - - - - - - - 0 1 000 0
FFDO Am9513 System
Read Data Register Write Data Register
1 1 - - - - - - - - 0 100 1 0
FFD2
Timing Controller Read Status Register Write Command Register
1 1 - - - - - - - - 0 1 100 0
HD8 Am9551 Serial Receive Data Buffer
Transmit Data Buffer
1 1 - - - - - - - - 0 1 1 0 1 0
FFDA I/O Port
#l
(P4)
Status Register Command Register
1 1 - - - - - - - - 100 000
FFEO
Am9551 Serial Receive Data Buffer Transmit Data Buffer
11- - - - - - - - 100 0 1 0
FFE2 I/O Port #2 (P5) Status Register Command Register
--
----
11- - - - - - - - 1 0 1 000
FFE8 Am8255A Read Port A
Write Port A
1 1 - - - - - - - - 101 010 FHA Parall el I/O Port Read Port B Write Port B
1 1 - - - - - - - - 1 0 0 100
FFEC Read Port C
Write Port C
1 1 - - - - - - - - 100 1 1 0
FFEE Status Register
COmmand Register
1 1 - - - - - - - - 1 1 100 0
FFFO Shadow ROM ON Write FFFO
1 1 - - - - - - - - 1 1 100 1
FFFl Shadow ROM OFF Write FFFl
BLOCK-SELECT MEMORY EXPANSION
Norma11 y, CPU add ress bi ts 0 to F (ADRO* to ADRF*) are used to add ress
up to 64K bytes of memory. Parallel I/O port C, bits 0 to 3, can be
used as additional address lines to expand memory addressing. Address
line ADF* is jumperable to either the CPU address output or one of the
port C bits. Figure 3-2111 ustrates one method of external memory
addressing. Note that the Multibus address line ADF* is connected to
port C bit O. Since the Am96/4116 has only 32K bytes on-board, the
ADF* line can be used to bank switch external memory. The scheme shown
in figure 3-2 permits up to eight external 64K byte RAM boards to be
used for a total of 512K bytes. Actually, external memory can be
either RAM or ROM, and is addressable in 32K-byte blocks. Blocks are
selected by programming bits 0 to 3 of port C.
ROM ADDRESSING
The Am96/4116 includes sockets for up to 8K bytes of ROM or EPROM. The
maximum storage for 2708 type devices is 2K bytes, for 2716 type
devices, 4K bytes, and for 2732 type devices 8K bytes.
A Shadow ROM
design permits ROM to be interchanged with RAM under program control.
3-2