I/O Addresses - NorthStar HSIO-4 User's & Technical Manual

3.1.3

I/O ADDRESSES

Port Address
A XOH
A X1H
A X2H
A X3H
X4H
B
X5H
B
B X6H
B X7H
C X8H
C X9H
XAH
C
C XBH
D XCH
D XDH
D XEH
D
XFH
North Star HSIO-4
The HSIO-4 requires 16 consecutive I/O
addresses. (All addresses referenced in this
section are I/O addresses.) Each of the four
ports uses four consecutive addresses.
Addresses start at XOH and run to XFH. (X
represents a hexadecimal digit which is set by
switches on the board.)
As can be seen in Table 3-1, port A starts at
XOH; port B starts at X4H; port C starts at
X8H; port D starts at XCH. The board address
space is used as follows:
Table 3-1
1Z£L PORT ADDRESS ASSIGNMENTS
Function
Baud rate select
Interrupt mask set
USART data
USART status/control
Baud rate select
Interrupt mask set
USART data
USART status/control
Baud rate select
Interrupt mask set
USART data
USART status/control
Baud rate select
Interrupt mask set
USART data
USART status/control
20
Port Access
write only
write only
read/write
read/write
write only
write only
read/write
read/write
write only
write only
read/write
read/write
write only
write only
read/write
read/write
User/Technical Manual