titus-larsen-titus-1981-apple-interfacing

scribed; the address bus signals, the data bus signals, and some of
the control signals. There are other useful signals provided at
seven available interface edge connectors. The signals are listed
described in Table 7-1.
Since you are already familiar with the data bus and address
signals, they will not be discussed any further. Some of the
signals are important, too, and they can be used to greatly
the construction of interface circuits.
1/0 SEl.ECi
The I/ 0 SELECT signal (pin 1) is active when it is a logic
as indicated by the "bar" above the same of the Each of
seven available interface slots, 1-7, has its own
thus this signal may be used to select a specific card. The
LECT signal for a card slot, n, is active when the address bus lines
are set at addresses CnOO through CnFF, inclusive. For example, if
the Apple addresses location C5AB, the J/ 0 SELECT signal at slot
5 will be a logic zero. None of the I/0 SELECT signals at the other
slots will be active at this time. There will also be times when none
of these signals is active. The range of addresses that affect the I/ 0
SELECT signals is shown in Table 7-2.
ini®rface Slo!'
A