Page 88 - DCAP210_INTRODUCTION__TO_MICROPROCESSORS

Introduction to Microprocessors

st
Notes The lower order address byte is present in the 1 clock of the machine cycle; it
must be latched (stored to hold the lower order address byte). V (Pin 20) is
ss
used for ground references.
V (Pin 40)
cc
An external DC supply voltage of +5V (17 milli-amps) is connected to this pin for the operation of
the 8085A as shown in Table 6.2.

Table 6.2: Pin description

Pin number Pin name Description Type

1, 2 X , X Crystal Input
1 2
3 Reset out Peripheral Reset Output Signal Output

4 SOD Serial output data Output
5 SID Serial Input data Input

6 TRAP Non-maskable interrupt Input
7 RST 7.5 Hardware vectored interrupt Input
8 RST 6.5 Hardware vectored interrupt Input

9 RST 5.5 Hardware vectored interrupt Input
10 INTR Interrupt Request Input

11 INTA Interrupt Acknowledgement Output
12-19 AD -AD Address/ Data Bus Bidirectional,
0 7
tristate
20 V Ground Input
ss
21-28 A -A Address Bus (Higher byte) Output, tristate
8 15
29 S Bus state Output
0
30 ALE Address Latch Signal Output, tristate

31 WR Write control signal Output, tristate
32 RD Read control signal Output, tristate
33 S Bus state Output
1
34 IO/M I/O or memory status Output, tristate
35 READY Wait state request Input

36 RESET IN System Reset Input
37 CLK (OUT) Clock signal Outpu
38 HLDA Hold Acknowledgment Output

39 HOLD Hold Request Input
40 V (+5V) Power
cc

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