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I/O Ad dress
Off set
00H
01H
02H
03H
04H
05H
06H
07H
08H
09H
0AH
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. Writing a '0' to a bit position causes the corresponding output pin to go to a High-Impedance
state (pulled high by external 10K ohm resistors). 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
Bits 5-0 al low for lock ing the I/O ports. A '1' writ ten to the I/O port po si tion will pro hibit fur ther
writes to the cor re spond ing I/O port.
030530
WinSystems - "The Embedded Authority"
Page 0
Port 0 I/O
Port 0 I/O
Port 1 I/O
Port 1 I/O
Port 2 I/O
Port 2 I/O
Port 3 I/O
Port 3 I/O
Port 4 I/O
Port 4 I/O
Port 5 I/O
Port 5 I/O
Int_Pend ing
Int_Pend ing
Page/Lock
Page/Lock
N/A
N/A
N/A
EBC-LP OPERATIONS MANUAL
Page 1
Page 2
Port 0 I/O
Port 1 I/O
Port 2 I/O
Port 3 I/O
Port 4 I/O
Port 5 I/O
Int_Pend ing
Page/Lock
Pol_0
Enab_0
Pol_1
Enab_1
Pol_2
Enab_2
Page 3
Port 0 I/O
Port 1 I/O
Port 2 I/O
Port 3 I/O
Port 4 I/O
Port 5 I/O
Int_Pend ing
Page/Lock
Int_ID0
Int_ID1
Int_ID2
Page 2-21
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