Parallel Input/Output (I/O) Ports
Parallel I/O Control Register
MC68HC11E Family
—
Rev. 4
Technical Data
MOTOROLA
Parallel Input/Output (I/O) Ports
141
6.9 Parallel I/O Control Register
The parallel handshake functions are available only in the single-chip
operating mode. PIOC is a read/write register except for bit 7, which is
read only.
Table 6-2
shows a summary of handshake operations.
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
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)