Datasheet

Table Of Contents
MC68HC908GP20Rev 2.1 Advance Information
Freescale Semiconductor 209
Table 15-1. Monitor Mode Signal Requirements and Options
IRQ RESET
$FFFE/
$FFFF
PLL PTC0 PTC1 PTC3
External
Clock
(1)
CGMOUT
Bus
Frequency
COP
For Serial
Communication
Comment
PTA0 PTA7
Baud
Rate
(2)
(3)
X GND X X X X X X 0 0 Disabled X X 0 No operation until
reset goes high
V
TST
V
DD
or
V
TST
X OFF 1 0 0 4.9152
MHz
4.9152
MHz
2.4576
MHz
Disabled 1 0 9600 PTC0 and PTC
voltages only
required if
IRQ
= V
TST
;
PTC3 determines
frequency divider
X 1 DNA
V
TST
V
DD
or
V
TST
X OFF 1 0 1 9.8304
MHz
4.9152
MHz
2.4576
MHz
Disabled 1 0 9600 PTC0 and PTC1
voltages only
required if
IRQ
= V
TST
;
PTC3 determines
frequency divider
X 1 DNA
V
DD
V
DD
$0000 OFF X X X 9.8304
MHz
4.9152
MHz
2.4576
MHz
Disabled 1 0 9600 External frequency
always divided by 4
X 1 DNA
GND V
DD
$0000 ON X X X 32.768
kHz
4.9152
MHz
2.4576
MHz
Disabled 1 0 9600 PLL enabled
(BCS set)
in monitor code
X 1 DNA
V
DD
or
GND
V
TST
$0000 OFF X X X X Enabled X X Enters user
mode — will
encounter an illegal
address reset
V
DD
or
GND
V
DD
or
V
TST
Non-zero OFF X X X X Enabled X X Enters user mode
Notes:
1. External clock is derived by a 32.768 kHz crystal or a 4.9152/9.8304 MHz off-chip oscillator
2. PTA0 = 1 if serial communication; PTA0 = X if parallel communication
3. PTA7 = 0serial, PTA7 = 1parallel communication for security code entry
4. DNA = does not apply, X = don’t care