titus-larsen-titus-1981-apple-interfacing

power buses, and that the proper connections are made to th
SN7400 chip.
The SN7 400 chip is used to gate the read/ write ( R/ W) signal wi
the main clock signal of the 6502 processor, Q°)l. This gating generat
the memory read signal, RD, and the memory write signal, WR. I
this gating is not done, the computer peripherals on the interface
breadboard will not work properly. In some computers, there
separate read and write signals. If you wish to use separate read
write signals for memory control in the Apple and other ""''"1-'''-'L'o•.
systems that are based on the 6502 microprocessor chip, you
generate them through the proper gating.
VECTOR 4609 CARD
INTERFACE
CONNECTOR
COMPONENT SIDE
(FRONT VIEW)
I \
24 25
\ I
::· )
!\
27 26
SIDE
The pin locations for the Vector card edge connectors are shown
in Fig. 5-13. Please note that this :Hgure shows the component side
of the card. Once you have made the needed connections between
the two edge connectors, and between the connectors and the
SN7 400, we suggest that you use an ohmmeter or other continuitychecking
instrument, to be sure that there are no short circuits between
adjacent and opposite pins, and that the correct connections
have been made. These tests should be made with the SN7 400 chip
out of its socket. However, don't forget to plug it back in after you
have tested the connections!
If you wish to try and interface some of the 6502 family interface
chips, and even some of the nonfamily chips, you will :find that these