MC68HC11A0CFN2(1996) Ver la hoja de datos (PDF) - Motorola => Freescale

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MC68HC11A0CFN2
(Rev.:1996)

HCMOS Single-Chip Microcontroller

Motorola => Freescale 

2.1.11.5 Port E

Port E is used for general-purpose inputs and/or analog-to-digital (A/D) input chan-

nels. Reading port E during the sampling portion of an A/D conversion could cause

very small disturbances and affect the accuracy of that result. If very high accuracy is

required, avoid reading port E during conversions.

2.2 Operating Modes

There are four operating modes for the MC68HC11A8: single-chip operating mode,

expanded multiplexed operating mode, special bootstrap operating mode, and special

test operating mode.

Table 2-1 shows how the operating mode is selected. The following paragraphs de-

scribe these operating modes.

2

2.2.1 Single-Chip Operating Mode

In single-chip operating mode, the MC68HC11A8 functions as a monolithic microcon-

troller without external address or data buses. Port B, port C, strobe A, and strobe B

function as general purpose l/O and handshake signals. Refer to 4 PARALLEL I/O for

additional information.

2.2.2 Expanded Multiplexed Operating Mode

In expanded multiplexed operating mode, the MC68HC11A8 has the capability of ac-

cessing a 64 Kbyte address space. This total address space includes the same on-

chip memory addresses used for single-chip operating mode plus external peripheral

and memory devices. The expansion bus is made up of port B and port C, and control

signals AS and R/W. Figure 2-4 shows a recommended way of demultiplexing low or-

der addresses from data at port C. The address, R/W, and AS signals are active and

valid for all bus cycles including accesses to internal memory locations.

MOTOROLA

2-6

SIGNAL DESCRIPTIONS AND OPERATING MODES

MC68HC11A8

TECHNICAL DATA

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