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Development Support
MC68HC908QY/QT Family Data Sheet, Rev. 5
142
Freescale Semiconductor
The rising edge of the internal RST signal latches the monitor mode. Once monitor mode is latched, the
values on PTA1 and PTA4 pins can be changed.
Once out of reset, the MCU waits for the host to send eight security bytes (see
15.3.2 Security). After the
security bytes, the MCU sends a break signal (10 consecutive logic 0s) to the host, indicating that it is
ready to receive a command.
15.3.1.1 Normal Monitor Mode
RST and OSC1 functions will be active on the PTA3 and PTA5 pins respectively as long as VTST is
applied to the IRQ pin. If the IRQ pin is lowered (no longer VTST) then the chip will still be operating in
monitor mode, but the pin functions will be determined by the settings in the configuration registers (see
BIL instructions will read the IRQ pin state only if IRQEN is set in the CONFIG2 register.
Table 15-1. Monitor Mode Signal Requirements and Options
Mode
IRQ
(PTA2)
RST
(PTA3)
Reset
Vector
Serial
Communi-
cation
Mode
Selection
COP
Communication
Speed
Comments
PTA0
PTA1 PTA4
External
Clock
Bus
Frequency
Baud
Rate
Normal
Monitor
VTST
VDD
X1
1
0
Disabled
9.8304
MHz
2.4576
MHz
9600
Provide external
clock at OSC1.
Forced
Monitor
VDD
X
$FFFF
(blank)
1X
X
Disabled
9.8304
MHz
2.4576
MHz
9600
Provide external
clock at OSC1.
VSS
X
$FFFF
(blank)
1X
X
Disabled
X
3.2 MHz
(Trimmed)
9600
Internal clock
is active.
User
X
Not
$FFFF
X
Enabled
X
MON08
Function
[Pin No.]
VTST
[6]
RST
[4]
—
COM
[8]
MOD0
[12]
MOD1
[10]
—
OSC1
[13]
——
1. PTA0 must have a pullup resistor to VDD in monitor mode.
2. Communication speed in the table is an example to obtain a baud rate of 9600. Baud rate using external oscillator is bus
frequency / 256 and baud rate using internal oscillator is bus frequency / 335.
3. External clock is a 9.8304 MHz oscillator on OSC1.
4. X = don’t care
5. MON08 pin refers to P&E Microcomputer Systems’ MON08-Cyclone 2 by 8-pin connector.
NC
1
2
GND
NC
3
4
RST
NC
5
6
IRQ
NC
7
8
PTA0
NC
9
10
PTA4
NC
11
12
PTA1
OSC1
13
14
NC
VDD
15
16
NC