HC05 datasheet(25/232 Pages) MOTOROLA

25 / 232 page

MC68HC05X16

Rev. 1

MOTOROLA

2-1

MODES OF OPERATION AND PIN DESCRIPTIONS

MODES OF OPERATION AND

PIN DESCRIPTIONS

2.1

Modes of operation

The MC68HC05X16 MCU has two modes of operation, single-chip mode and bootstrap mode. In

the MC68HC05X16 the single-chip mode is the normal user operating frequency Table 2-1 shows

the conditions required to enter each mode on the rising edge of RESET.

Note:

On the rising edge of RESET, holding the IRQ pin at 2 x VDD is equivalent to holding

the MDS pin at VDD. The device cannot enter single-chip mode unless MDS is tied to

VSS (or left ﬂoating) and IRQ is below VDD.

2.1.1

Single-chip mode

This is the normal user operating mode of the MC68HC05X16. In this mode the device functions

as a self-contained microcomputer (MCU) with all on-board peripherals, including the three 8-bit

I/O ports and the 8-bit input-only port, available to the user. All address and data activity occurs

within the MCU.

Table 2-1 Mode of operation selection

MDS

IRQ

TCAP1

TCAP2

PD3

PD4

Mode

VSS

AND

VSS to VDD

Single-chip

VDD

2VDD

VSS

Reserved for Motorola use

Bootstrap mode:

VDD

2VDD

VDD

VSS

Serial RAM loader

VDD

2VDD

VDD

VSS

Jump to RAM + 1

VDD

2VDD

VDD

VSS

Jump to any address

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