
M68HC11E Family Data Sheet, Rev. 5.1
Freescale Semiconductor
97
Chapter 6
Parallel Input/Output (I/O) Ports
6.1 Introduction
All M68HC11 E-series MCUs have five input/output (I/O) ports and up to 38 I/O lines, depending on the
operating mode. Refer to
Table 6-1 for a summary of the ports and their shared functions.
Port pin function is mode dependent. Do not confuse pin function with the electrical state of the pin at
reset. Port pins are either driven to a specified logic level or are configured as high-impedance inputs. I/O
pins configured as high-impedance inputs have port data that is indeterminate.
In port descriptions, an I indicates this condition. Port pins that are driven to a known logic level during
reset are shown with a value of either 1 or 0. Some control bits are unaffected by reset. Reset states for
these bits are indicated with a U.
Table 6-1. Input/Output Ports
Port
Input
Pins
Output
Pins
Bidirectional
Pins
Shared Functions
Port A
3
2
Timer
Port B
—
8
—
High-order address
Port C
—
8
Low-order address and data bus
Port D
—
6
Serial communications interface (SCI)
and serial peripheral interface (SPI)
Port E
8
—
Analog-to-digital (A/D) converter