Apple Lisa - The System Bus

Confidential
Lisa Hardware Reference Manual
THE SYSTEM BUS
The system bus connects the CPU board, I/O board, and expansion
slots, providing a simple interface between the various devices.
When an address is put on the bus, a signal indicates the start of
the cycle. The system then waits for the addressed device to respond
with the acknowledge signal which marks the end of the cycle. Timing
on the system bus is non-critical. The bus cycle can be as short as
800 nanoseconds or as long as SO microseconds. If the addressed
device does not respond within 50 microseconds, a timer on the bus
asserts the bus error signal. A detailed description of the System
Bus timing is given in the· section on the expansion I/O slots.
The following pages describe in detail the CPU board and memory
management unit, the various built-in I/O devices and interfaces, and
the expansion slots. A discussion of the design of device drivers
can be found in the Operating System Reference Manual. This manual
is intended for programmers who deal directly with thehardware--it
is not a service manual. nor does it provide a complete theory of
operation. Complete schematics are included; however. in the
appendices.
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7-Jul-81