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| MC68HC05SR3 Datasheet, PDF (73/96 Pages) Freescale Semiconductor, Inc – High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcontroller Units | |||
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10
OPERATING MODES
The MC68HC05SR3/MC68HC705SR3 has two modes of operation: the User Mode and the
Self-Check/Bootstrap Mode. Table 10-1 shows the conditions required for entering the two
operating modes.
RESET
5V
VTST = 2 Ã VDD
Table 10-1 Mode Selection
VPP
VSS to VDD
VTST
PB1
VSS to VDD
VDD
MODE
USER
SELF-CHECK/BOOTSTRAP
10.1
User Mode
The normal operating mode of the MC68HC05SR3/MC68HC705SR3 is the User mode. This
mode is entered on the rising edge of RESET when the VPP and PB1 pins are between VSS and
VDD.
10
10.2
Self-Check Mode
The Self-check mode is provided on the MC68HC05SR3 for the user to check device functions
with an on-chip self-check program masked at location $1F00 to $1FEF under minimum hardware
support. The self-check schematic is shown in Figure 10-1. Self-check mode is entered on the
rising edge of RESET when the VPP pin is at VTST (2ÃVDD) and PB1 pin is at VDD. Once in the
self-check mode, PB1 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 LEDsâ
on-off pattern can show what part of the device is suspected to be bad. Table 10-2 lists the LEDsâ
on-off patterns and their corresponding indications.
MC68HC05SR3
OPERATING MODES
TPG
Freescale
10-1
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