mc68hc05bs8 Freescale Semiconductor, Inc, mc68hc05bs8 Datasheet - Page 121

• Manufacturer Part Number: mc68hc05bs8
• Description: Mc68hc05 Family Of Low-cost Single-chip Microcontrollers.
• Manufacturer: Freescale Semiconductor, Inc

A.3
The MC68HC705BS8 also has two modes of operation – user mode and EPROM bootstrap
mode. Table A-1 shows the conditions required to enter each mode on the rising edge of RESET.
A.3.1
The normal operating mode of the MC68HC705BS8 is the user mode. The user mode will be
entered if the RESET line is brought low, and the IRQ pin is within its normal operational range
(V
Warning: In the MC68HC705BS8, all vectors are fetched from EPROM in user mode; therefore,
A.3.2
The bootstrap mode is provided in the MC68HC705BS8 as a mean of self-programming its
EPROM with minimal circuitry. It is entered on the rising edge of RESET if IRQ pin is at 1.8V
and PB6 is at logic one. RESET must be held low for 4064 cycles after POR (power-on reset).
A.4
The Program Control register (PCR) is provided for EPROM programming. The function of the
EPROM depends on the device operating mode.
MC68HC05BS8
SS
to V
DD
the EPROM must be programmed (via the bootstrap mode) before the device is
powered up in user mode.
* Minimum hold time should be 2 clock cycles, after that it can be used as a normal IRQ function pin.
), the rising edge of the RESET will cause the MCU to enter the user mode.
Modes of Operation
User Mode
Bootstrap Mode
EPROM Programming
RESET
5V
5V
Table A-1 MC68HC705BS8 Operating Mode Entry Conditions
9V
V
+9V Rising Edge*
SS
IRQ
to V
DD
MC68HC705BS8
V
SS
PB6
V
to V
DD
DD
BOOTSTRAP
MODE
USER
TPG
DD
A