MC908QT4MPE datasheet(142/184 Pages) FREESCALE

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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

Chapter 5 Configuration Register (CONFIG)) when VTST was lowered. With VTST lowered, the BIH and

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

Disabled

9.8304

MHz

2.4576

MHz

9600

Provide external

clock at OSC1.

Forced

Monitor

VDD

$FFFF

(blank)

Disabled

9.8304

MHz

2.4576

MHz

9600

Provide external

clock at OSC1.

VSS

$FFFF

(blank)

Disabled

3.2 MHz

(Trimmed)

9600

Internal clock

is active.

User

Not

$FFFF

Enabled

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.

GND

RST

IRQ

PTA0

PTA4

PTA1

OSC1

VDD

MC908QT4MPE Datasheet(PDF) 142 Page - Freescale Semiconductor, Inc

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