MOTOROLA
13-2
MC68HC05T16
OPERATING MODES
13
13.1
User Mode (Normal Operation)
The normal operating mode of the MC68HC05T16/
MC68HC705T16 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
SS
to V
DD
), the rising edge of the RESET will cause the MCU to enter the user
mode.
13.2
Self-Check Mode
The MC68HC05T16 self-check mode is for the user to check device functions with an on-chip
self-check program masked at location $FE00 to $FFEF under minimum hardware support. The
hardware is shown in Figure 13-3. Figure 13-2 is the criteria to enter self-check mode, where
PC2’s condition is latched within first two clock cycles after the rising edge of the reset. PC2 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 can show
what part of the device is suspected to be bad. Table 13-2 lists the LEDs’ on-off patterns and their
corresponding indications.
Table 13-1 Mode Selection
RESET
IRQ
PC2
MODE
V
SS
to V
DD
V
SS
to V
DD
USER
+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 IRQ function pin.
Figure 13-2 Self-Check Mode Timing
5V
5V
9V
PC2
IRQ
RESET
+5V
+5V
+9V
TPG
110
Summary of Contents for MC68HC05T16
Page 2: ......
Page 14: ...MOTOROLA vi MC68HC05T16 THIS PAGE LEFT BLANK INTENTIONALLY TPG 12 ...
Page 16: ...MOTOROLA viii MC68HC05T16 THIS PAGE LEFT BLANK INTENTIONALLY TPG 14 ...
Page 18: ...MOTOROLA x MC68HC05T16 THIS PAGE LEFT BLANK INTENTIONALLY TPG 16 ...
Page 54: ...MOTOROLA 5 12 MC68HC05T16 TIMERS 5 THIS PAGE LEFT BLANK INTENTIONALLY TPG 52 ...
Page 64: ...MOTOROLA 6 10 MC68HC05T16 M BUS SERIAL INTERFACE 6 THIS PAGE LEFT BLANK INTENTIONALLY TPG 62 ...
Page 110: ...MOTOROLA 12 4 MC68HC05T16 LOW POWER MODES 12 THIS PAGE LEFT BLANK INTENTIONALLY TPG 108 ...
Page 116: ...MOTOROLA 13 6 MC68HC05T16 OPERATING MODES 13 THIS PAGE LEFT BLANK INTENTIONALLY TPG 114 ...