HC705E5GRSSLASHD datasheet(52/148 Pages) NXP

52 / 148 page

Input/Output (I/O) Ports

General Release Specification

MC68HC705E5 — Rev. 1.0

Input/Output (I/O) Ports

7.4 Port B

Port B is an 8-bit bidirectional port which does share some of its pins with

other subsystems. The address of the port B data register is $0001 and

the DDR is at address $0005. Reset does not affect the data registers,

but clears the data direction registers, thereby returning the ports to

inputs. Writing a one to a DDR bit sets the corresponding port bit to

output mode. Refer to Section 11. Motorola Bus (M Bus) Interface and

Section 12. Synchronous Serial Interface (SSI) for descriptions of

port B behavior while either module is enabled.

7.5 Port C

Port C is a 4-bit bidirectional port which does not share any of its pins

with other subsystems. The port C data register is at $0002 and the DDR

is at $0006. Reset does not affect the data registers, but clears the data

direction registers, thereby returning the ports to inputs. Writing a one to

a DDR bit sets the corresponding port bit to output mode.

7.6 Input/Output Programming

Ports A, B, and C may be programmed as inputs or outputs under

software control. The direction of the pins is determined by the state of

the corresponding bit in the port DDR with each port having an

associated DDR. Any port A, port B, or port C pin is configured as an

output if its corresponding DDR bit is set to a logic 1. A pin is configured

as an input if its corresponding DDR bit is cleared to a logic 0.

At power-on or reset, all DDRs are cleared, which configures all port A,

B, and C pins as inputs. The data direction registers are capable of being

written to or read from by the processor. During the programmed output

state, a read of the data register actually reads the value of the output

data latch and not the I/O pin. See Table 7-1 and Figure 7-1.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

HC705E5GRS/D 데이터시트(PDF) 52 Page - NXP Semiconductors