M68ICS08KX datasheet(35/77 Pages) MOTOROLA

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Support Information

KXICS Theory of Operation

M68ICS08KX In-Circuit Simulator

User’s Manual

MOTOROLA

Support Information

When the jumper is set for the PTB6 position, the MCU runs from it’s internal

clock and pin PTB6 of the MCU is connected to the target connector.

When the jumper is set for the CLK position, the Y1 external clock signal from

the KXICS board is applied to the PTB6 pin of the MCU for timing. (An internal

MCU register must be set to control the selection of internal or external clock.)

The external clock, Y1, has an output frequency of 9.8304 MHz to allow the

MCU to communicate at 9600 baud. It is socketed to allow the use of a full-size

or half-size clock. You may change clock frequencies by installing a new clock

chip, however the serial communication rate proportionally changes. W3 may

be used to disable the external clock.

Additionally, the on-board clock is available as an output on the 3-pin header J4

for target or computer host clock synchronization.

3.4.4 Start-Up in Monitor Mode

Following power up the ICS_RST# is held low for a period of time by U8.

When ICS_RST* is asserted high, the binary ripple counter, U3, counts up 1024

clock cycles prior to allowing DELAY RESET to be asserted. The delayed reset

controls the analog switch, U7, connected to PTA1 and PTB[0...1]. The RTS

signal is held high which places the VTST voltage as the high voltage for IRQ*.

Analog switch, U7, connects PTA1 to common, PTB0 to VDD_MCU, and PTB1

to common until DELAY_RESET is asserted. VTST is held above VDD-MCU

+3Vdc during the reset release forcing the KXICS board to power up in the

Monitor Mode.

Following the counter time-out, the analog switch, U7, is toggled so that the

PTA1 and PTB[0...1] pins of the board are connected to the target head

connectors.

Following entry into monitor mode, you may switch the IRQ* voltage to

VDD_MCU by setting RTS low. The analog switch, U14, will switch the

connection of MCU pin 9 from the ICS reset circuitry to a connection to the

target head connector. Be aware that beside disabling the use of external resets

of the MCU, internal MCU features, e.g., the COP must be serviced properly in

this mode.

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