xr88c681 Exar Corporation, xr88c681 Datasheet - Page 46

• Manufacturer Part Number: xr88c681
• Description: Cmos Dual Channel Uart Duart
• Manufacturer: Exar Corporation

C.6.2.2 8086 Microprocessor
The 8086 microprocessor is a 16 bit microprocessor manufactured by Intel Corporation. Figure 20 presents the pin out
diagram of this IC. Please note that in Figure 20, pins 24 - 31 have some additional labels, located off to the right of the
package. These additional labels will be explained later in this text.
Intel went to great lengths to keep the pin count of this IC
low by multiplexing the functions of many of these pins.
This device consists of a 16 bit Data Bus and a 20 bit
Address Bus. The Data Bus is multiplexed with the lower
16 Address Bits (A0 - A15) to form AD0 - AD15. Address
Rev. 2.11
Figure 20. Pin Out of the 8086 Microprocessor Device
AD14
AD13
AD12
AD11
AD10
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
NMI
INTR
CLK
GND
GND
10
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
9
8086 CPU
46
Bits A16 - A19 are multiplexed with status bits S3 - S6 to
form A16/S3, A17/S4, A18/S5 and A19/S6. All of these
pins are address lines during the first half of a memory
cycle. However, during the second half of a memory
cycle, these pins then take on their alternate functions
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
-RQ/-GT1
-LOCK
-S2
-S1
V
AD15
A16/S3
A17/S4
A18/S5
A19/S6
-BHE/S7
MN/MX
-RD
-TEST
READY
RESET
-RQ/-GT0
-S0
QS0
QS1
CC
(-DEN)
(HOLD)
(HLDA)
(-WR)
(M/-IO)
(DT/-R)
(-INTA)
(ALE)