Motorola MVME1603, Installation And Use Manual

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Block Diagram
3-14
3
The SNAPHAT battery package is mounted on top of the MT48T18
device. The battery housing is keyed to prevent reverse insertion.
The clock furnishes seconds, minutes, hours, day, date, month, and year in
BCD 24-hour format. Corrections for 28-, 29- (leap year), and 30-day
months are made automatically. The clock generates no interrupts.
Although the M48T18 is an 8-bit device, 8-, 16-, and 32-bit accesses from
the ISA bus to the M48T18 are supported. Refer to the
MVME1603/MVME1604 Programmer’s Reference Guide and to the
M48T18 data sheet for detailed programming and battery life information.
Programmable Timers
Among the resources available to the local processor are a number of
programmable timers. Timers are incorporated into the ISA bridge
controller, the Z8536 CIO device (diagrammed in Figure 1-1 and Figure 1-
2 for the two base boards), and the VMEchip2. They can be programmed
to generate periodic interrupts to the processor.
Interval Timers
The ISA bridge controller has three built-in counters that are equivalent to
those found in an 82C54 programmable interval timer. These counters are
grouped into one timer unit, Timer 1, in the IBC. Each counter output has
a specific function:
❏
Counter 0 is associated with interrupt request line IRQ0. It can be
used for system timing functions, such as timer interrupt for a time-
of-day.
❏
Counter 1 generates a refresh request signal for ISA memory. This
timer is not used in the MVME1603/MVME1604.
❏
Counter 2 provides the tone for the speaker output function on the
ISA bridge controller (the
SPEAKER_OUT
signal which can be
cabled to an external speaker via the remote reset connector).
The interval timers use the OSC clock input as their clock source. The
MVME1603/MVME1604 module drives the OSC pin with a 14.31818
MHz clock source.