Chapter 5 Hardware Description; Introduction; General Description; Microcontroller - Motorola M68HC11EVBU User Manual

5.1

INTRODUCTION

This chapter provides an overall general description of the EVBU hardware. This description is
supported by a simplified block diagram (Figure 5-1). The EVBU schematic diagram, located in
Chapter 6, can also be referred to for the following descriptions.
5.2

GENERAL DESCRIPTION

Overall evaluation/debugging control of the EVBU is provided by the BUFFALO monitor
program residing in the resident microcontroller (MCU) ROM. The wire-wrap area interface is
provided by the MCU device. RS-232C terminal I/O port interface circuitry provides
communication and data transfer operations between the EVBU and external terminal/host
computer devices.
5.2.1

Microcontroller

The EVBU resident M68HC11E9 MCU device (U3) is factory configured for the single-chip
mode of operation. The single-chip mode is accomplished by +5 Vdc applied to the MCU
MODB pin, and ground applied to the MCU MODA pin during reset.
The EVBU can be reconfigured for either the expanded-multiplexed, special-bootstrap, or
special-test modes of operation via jumper headers J3 and J4. For expanded-multiplexed and
special-test modes of operation, additional circuitry must be implemented on the EVBU wire-
wrap area to support the two modes. The EVBU can be reconfigured for the special-bootstrap
mode of operation without additional circuitry.
The MCU configuration (CONFIG) register (implemented in EEPROM) is programmed such
that the ROMON bit is set for EVBU operations. When this bit is set, MCU internal ROM is
enabled, and that memory space becomes internally accessed space. This allows the memory at
$D000-$FFFF to contain the BUFFALO monitor program.
The monitor program uses the MCU internal RAM located at $0048-$00FF. The control registers
are located at $1000-$103F.
M68HC11EVBU/D
CHAPTER 5
HARDWARE DESCRIPTION
HARDWARE DESCRIPTION
5-1