
Parallel Input/Output (I/O) Ports
Parallel I/O Control Register
M68HC11E Family — Rev. 5
Data Sheet
MOTOROLA
Parallel Input/Output (I/O) Ports
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115
STAF — Strobe A Interrupt Status Flag 
STAF is set when the selected edge occurs on strobe A. This bit can be cleared 
by a read of PIOC with STAF set followed by a read of PORTCL (simple strobed 
or full input handshake mode) or a write to PORTCL (output handshake mode). 
0 = No edge on strobe A 
1 = Selected edge on strobe A 
STAI — Strobe A Interrupt Enable Mask Bit
0 = STAF does not request interrupt 
1 = STAF requests interrupt 
CWOM — Port C Wired-OR Mode Bit (affects all eight port C pins)
It is customary to have an external pullup resistor on lines that are driven by 
open-drain devices.
0 = Port C outputs are normal CMOS outputs. 
1 = Port C outputs are open-drain outputs. 
HNDS — Handshake Mode Bit
0 = Simple strobe mode 
1 = Full input or output handshake mode 
OIN — Output or Input Handshake Select Bit
HNDS must be set to 1 for this bit to have meaning. 
0 = Input handshake 
1 = Output handshake 
Full-
output 
hand-
shake 
mode
Read 
PIOC with 
STAF = 1 
then write 
PORTCL
1
1
0 = STRB 
active level
1 = STRB 
active pulse
Driven as outputs if 
STRA at active 
level; follows 
DDRC 
if STRA not at 
active level
Normal output 
port, unaffected 
in handshake 
modes
Table 6-2. Parallel I/O Control (Continued)
STAF 
Clearing 
Sequence
HNDS
OIN
PLS
EGA
Port B
Port C
0
1
Port C
Driven
STRA
Active Edge
Follow
DDRC
Follow
DDRC
Address:
$1002
Bit 7
6
5
4
3
2
1
Bit 0
Read:
STAF
STAI
CWOM
HNDS
OIN
PLS
EGA
INVB
Write:
Reset:
0
0
0
0
0
U
1
1
U = Unaffected
Figure 6-10. Parallel I/O Control Register (PIOC)
F
Freescale Semiconductor, Inc.
n
.