I/O Ad dress
Offset
Page 0
Page 1
Page 2
Page 3
00H
Port 0 I/O
Port 0 I/O
Port 0 I/O
Port 0 I/O
01H
Port 1 I/O
Port 1 I/O
Port 1 I/O
Port 1 I/O
02H
Port 2 I/O
Port 2 I/O
Port 2 I/O
Port 2 I/O
03H
Port 3 I/O
Port 3 I/O
Port 3 I/O
Port 3 I/O
04H
Port 4 I/O
Port 4 I/O
Port 4 I/O
Port 4 I/O
05H
Port 5 I/O
Port 5 I/O
Port 5 I/O
Port 5 I/O
06H
Int_Pending
Int_Pending
Int_Pending
Int_Pending
07H
Page/Lock
Page/Lock
Page/Lock
Page/Lock
08H
N/A
Pol_0
Enab_0
Int_ID0
09H
N/A
Pol_1
Enab_1
Int_ID1
0AH
N/A
Pol_2
Enab_2
Int_ID2
Reg is ter De tails
Port 0-5 I/O - Each I/O bit in each of the 6 ports can be in di vidu ally pro grammed for in put or out
-
put. Writ ing a '0' to a bit po si tion causes the cor re spond ing out put pin to go to a High- Impedance state
(pulled high by ex ter nal 10K ohm re sis tors). This al lows it to be used as an in put. When used in the in put
mode, a read re flects the in verted state of the I/O pin, such that a high on the pin will read as a '0' in the
reg is ter. Writ ing a '1' to a bit po si tion causes the out put pin to sink cur rent (up to 12mA), ef fec tively
pull ing it low.
INT_PEND ING - This read- only reg is ter re flects the com bined state of the INT_ID0 through
INT_ID2 reg is ters. When any of the lower 3 bits are set, it in di cates that an in ter rupt is pend ing on the
I/O port cor re spond ing to the bit po si tion(s) that are set. Read ing this reg is ter al lows an In ter rupt Serv
-
ice Rou tine to quickly de ter mine if any in ter rupts are pend ing and which I/O port has a pend ing in ter
-
rupt.
PAGE/LOCK - This reg is ter serves two pur poses. The up per two bits se lect the reg is ter page in use
as shown here :
D7 D6 Page
0 0 Page 0
0 1 Page 1
1 0 Page 2
1 1 Page 3
991206
OPERATIONS MANUAL LBC-Plus
Page 2 - 23
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