Parallel Input/Output (I/O) Ports
Port E
MC68HC11E Family
—
Rev. 4
Technical Data
MOTOROLA
Parallel Input/Output (I/O) Ports
139
6.7 Port E
Port E is used for general-purpose static inputs or pins that share
functions with the analog-to-digital (A/D) converter system. When some
port E pins are being used for general-purpose input and others are
being used as A/D inputs, PORTE should not be read during the sample
portion of an A/D conversion.
6.8 Handshake Protocol
Simple and full handshake input and output functions are available on
ports B and C pins in single-chip mode. In simple strobed mode, port B
is a strobed output port and port C is a latching input port. The two
activities are available simultaneously.
The STRB output is pulsed for two E-clock periods each time there is a
write to the PORTB register. The INVB bit in the PIOC register controls
the polarity of STRB pulses. Port C levels are latched into the alternate
port C latch (PORTCL) register on each assertion of the STRA input.
STRA edge select, flag, and interrupt enable bits are located in the PIOC
register. Any or all of the port C lines can still be used as
general-purpose I/O while in strobed input mode.
Address:
$100A
Bit 7
6
5
4
3
2
1
Bit 0
Read:
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
Write:
Reset:
Indetermnate after reset
Alternate Function:
AN7
AN6
AN5
AN4
AN3
AN2
AN1
AN0
Figure 6-9. Port E Data Register (PORTE)