Real Time Devices AD1200 User Manual page 22

Table 1-2- Base Address Swltch Settlngs, S1
Base Address
Decimal/ (Hex)
Swltch Setting
5 4 3 2 1
Base Address
Decimal/ (Hex)
Switch Settlng
5 4 3 2 ' l
sn tQ00)
0 0 0 0 0
768 / (300)
1 0 0 0 0
s28 | (2ro)
0 0 0 0 1 784 tQr0)
1 0 0 0 1
su t(220)
0 0 0 1 0
8oo / (320)
1 0 0 1 0
s60 tQ30) 0 0 0 1 1
-816 / (330)
1 0 0 1 1
576 | (240) 0 0 1 0 0 832 | (340)
1 0 1 0 0
s92 tQs0)
0 0 1 0 1
848 / (350)
1 0 1 0 1
608 tQ60) 0 0 1 1 0 864 / (360)
1 0 1 1 0
6U tQ70)
0 0 1 1 1
880 / (370)
1 0 1 1 1
640 | (280)
0 1 0 0 0 896 / (380)
1 1 0 0 0
6s6 | (290)
0 1 0 0 1
en tQn)
l l 0 0 l
672 t QA0) 0 1 0 1 0 928 / (3A0)
1 1 0 1 0
688 / (2B0)
0 1 0 1 1 9M t(380)
l l 0 l l
704 tQC0)
0 1 1 0 0 960 / (3C0)
1 1 1 0 0
720 tQm)
0 1 1 0 1 976 tQrn)
1 1 1 0 1
736 t(2E0)
0 1 1 1 0 9e2 t(3E0)
1 1 1 1 0
7s2 | (2F0)
0 l t l l
1008 / (3F0)
1 1 1 1 1
0 = c l o s e d , 1 = o p e n
Pull-up/Pull-down Resistors on Digital VO Lines
The 8255 programmable peripheral inrerface provides 16 TTI/CMOS compatible digiral VO lines which can be
interfaced with external devices. These lines are divided into three groups: eight Port A lines, four port C Lower
lines, and four Port C Upper lines. (The eight lines of Port B are used for internal board functions.) You can insall
and connect pull-up or pull-down resistors for any or all of these three groups of lines. You may want to pull lines
up for connection to switches. This will pull the line high when the switch is disconnected. Or, you may want to pull
lines down for connection to relays which control urning motors on and off. These motors turn on when the digitat
lines controlling them are high. The Port A line.s of the 8255 automatically power up as inputs, which can float high
during the few moments before the board is first initialized. This can cause the external devices connected to these
lines to operate erratically. By pulling these lines down, when the data acquisition system is first hrned on, the
motors will not switch on before the 8255 is initialized.
To use the pull-up/pull-down feature, you must first ins0all 10 kilohm resistor packs in any or all of the three
locations near the 8255, labeled PA, PCL, and PCH. PA akes a lGpin pack, and PCL and PCH take 6-pin packs.
Figure 1- l5 shows a blowup of the PA, PCL, and PCH resistor pack locations.
After the resistor packs are installed, you must connect them into ttre circuit as pull-ups or pull-downs. Locate
the three-hole pads on ttre board below the resistor packs. They are labeled G (for ground) on one end and V (for
+5V) on the other end. The middle hole is common. PA is for Port A, PCL is for Port C Lower, and pCH is for port
C Upper. Figure l-15 shows ttrese pads. To operate as pull-ups, solder a jumper wire between the common pin
(middle pin of tlre three) and the V pin. For pull-downs, solder a jumper wire berween tlre common pin (middle pin)
and the G pin. Figure l-16 shows Port A lines with pull-ups, Port C lower with pull-downs, and Port C Upper with
no resistors.
l - 1 0