MC68HC05F8 Datasheet, PDF (106/126 Pages) Motorola, Inc – High-density complementary metal oxide semiconductor(HCMOS) microcontroller unit

Freescale Semiconductor, Inc.
Table 12-1 Mode Selection
RESET
IRQ1
TCAP
MODE
5V
V_SS to V_DD
V_SS to V_DD
USER
5V
9V
+9V Rising Edge*
V_DD
SELF-CHECK/
BOOTSTRAP
* Minimum hold time should be 2 clock cycles, after that it can be used as a normal IRQ1
function pin.
12.1
User Mode (Normal Operation)
The normal operating mode of the MC68HC05F8/MC68HC705F8 is the user mode. The user
mode is entered if the RESET line is brought low, and the IRQ1 pin is within its normal operating
range (V_SS to V_DD), the rising edge of the RESET will cause the MCU to enter the user mode.
12.2
Self-Check Mode
The self-check mode is available on the MC68HC05F8 only, and is for the user to check device
functions with an on-chip self-check program masked at location $FE00 to $FEDF under minimum
hardware support. The self-check circuit is shown in Figure 12-3. Figure 12-2 is the criteria to
enter self-check mode, where TCAP’s condition is latched within first two clock cycles after the
rising edge of the reset. TCAP can then be used for other purposes. After entering the self-check
mode, CPU branches to the self-check program and carries out the self-check. Self-check is a
repetitive test, i.e. if all parts are checked to be good, the CPU will repeat the self-check again.
Therefore, the LEDs attached to Port A will be flashing if the device is good; else the combination
of LEDs’ on-off pattern will indicate which part of the device is suspected to be bad. Table 12-2
lists the LEDs’ on-off patterns and their corresponding indications.
12
+5 V
TCAP
+9 V
IRQ1
+5 V
RESET
Figure 12-2 Self-Check Mode Timing
MOTOROLA
12-2
OPERATING MODES
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MC68HC05F8