Chapter 8
8051 Hardware Connection and Intel
Hex File
1
Objective
• 這章節要去了解8051每個角位的意義與用法。
• 另外也要了解Intel Hex File的規格。
2
Sections
8.1 Pin description of the 8051
8.2 Design and test of DS89C4x0 timer
8.3 Explaining the Intel hex file
3
Section 8.1
Pin Description of the 8051
4
Packing Types of 8051
• The 8051 family members come in different
packages, such as DIP（Dual In-line
Package）,QFP（Quad Flat Package）and LCC
（Leadless Chip Carrier）.
– See Appendix H（Pages 621-623）
– PDIP（Plastic DIP）& CERDIP（Ceramic DIP）
• They all have 40 pins.
• Figure 8-1. 8051 Pin Diagram
– Also for 8052, 8031, DS89C4x0, AT89C51
5
Figure 8-1. 8051 Pin Diagram
PDIP/CERDIP
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
RST
(RXD)P3.0
(TXD)P3.1
(INT0)P3.2
(INT1)P3.3
(T0)P3.4
(T1)P3.5
(WR)P3.6
(RD)P3.7
XTAL2
XTAL1
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
8051
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
Vcc
P0.0(AD0)
P0.1(AD1)
P0.2(AD2)
P0.3(AD3)
P0.4(AD4)
P0.5(AD5)
P0.6(AD6)
P0.7(AD7)
EA/VPP
ALE/PROG
PSEN
P2.7(A15)
P2.6(A14)
P2.5(A13)
P2.4(A12)
P2.3(A11)
P2.2(A10)
P2.1(A9)
P2.0(A8)
6
Pins of 8051（1/5）
• Vcc（pin 40）：
– Vcc provides supply voltage to the chip.
– The voltage source is +5V.
• GND（pin 20）：ground
• XTAL1 and XTAL2（pins 19,18）：
–
–
–
–
These 2 pins provide external clock.
Way 1：using a quartz crystal oscillator 
Way 2：using a TTL oscillator 
Example 8-1 shows the relationship between XTAL and
the machine cycle. 
7
Pins of 8051（2/5）
• I/O port pins
– The four ports P0, P1, P2, and P3. 
– Each port uses 8 pins.
– All I/O pins are bi-directional.
8
Pins of 8051（3/5）
• RST（pin 9）：reset
– It is an input pin and is active high（normally low）.
• The high pulse must be high at least 2 machine cycles.
– It is a power-on reset.
• Upon applying a high pulse to RST, the microcontroller will
reset and all values in registers will be lost.
• Reset values of some 8051 registers 
– Way 1：Power-on reset circuit 
– Way 2：Power-on reset with debounce 
9
Pins of 8051（4/5）
• /EA（pin 31）：external access
– There is no on-chip ROM in 8031 and 8032 .
– “/” means active low.
– The /EA pin is connected to GND to indicate the code
is stored externally. 
– For 8051, /EA pin is connected to Vcc. 
– /PSEN ＆ ALE are used for external ROM too.
• /PSEN（pin 29）：program store enable
– This is an output pin and is connected to the OE pin of
the ROM. 
– See Chapter 14.
10
Pins of 8051（5/5）
• ALE（pin 30）：address latch enable 
– 8051 port 0 provides both address and data.
– The ALE pin is used for de-multiplexing the address
and data by connecting to the G pin of the 74LS373
latch.
– It is an output pin and is active high.
• When ALE=1, P0 provides address A0-A7.
• When ALE=0, P0 provides data D0-D7.

11
Figure 8-2 (a). XTAL Connection to 8051
• Using a quartz crystal oscillator
• We can observe the frequency on the XTAL2 pin.
C2
)|
30pF
XTAL2
C1
)|
30pF
XTAL1
GND

12
Figure 8-2 (b). XTAL Connection to an
External Clock Source
• Using a TTL oscillator
• XTAL2 is unconnected.
NC
EXTERNAL
OSCILLATOR
SIGNAL
XTAL2
XTAL1
GND

13
Example 8-1
Find the machine cycle (MC) for the following chip if
XTAL = 11.0592 MHz
(a) AT89C51
(b) DS89C4x0
(c) DS5000
Solution:
1/11.0592 MHz = 90.42 ns
(a) 1 MC = 90.42 ns  12 = 1.085 s
(b) 1 MC = 90.42 ns  1 = 90.42 ns
(c) 1 MC = 90.42 ns  4 = 361.68 ns

14
Port 0（pins 32-39）
• P0 is an open drain.
– Open drain is a term used for MOS chips in the same
way that open collector is used for TTL chips.
• When P0 is used for simple data I/O, we must
connect it to external pull-up resistors.
– Each pin of P0 must be connected externally to a 10K
ohm pull-up resistor.
– With external pull-up resistors connected upon reset,
port 0 is configured as an output port.
• When P0 is used for address/data multiplexing, it
is connected to the 74LS373 to latch the address.
15
Figure 8-4. Port 0 with Pull-Up Resistors
Vcc
Port
P0.0
DS5000 P0.1
P0.2
8751 P0.3
8951 P0.4
P0.5
P0.6
P0.7
10 K
0
16
Port 1（pins 1-8）
• Port 1 does not need any pull-up resistors since it
already has pull-up resistors internally.
• Usually used for I/O.
17
Port 2（pins 21-28）
• Port 2 does not need any pull-up resistors since it
already has pull-up resistors internally.
• In an 8031-based system, P2 are used to provide
address A8-A15.
18
Port 3（pins 10-17）
• Port 3 does not need any pull-up resistors since it
already has pull-up resistors internally.
• Port 3 has the additional function of providing
signals.
–
–
–
–
Serial communications signal：RxD, TxD（Chapter 10）
External interrupt：/INT0, /INT1（Chapter 11）
Timer/counter：T0, T1（Chapter 9）
External memory accesses in 8031-based system：/WR,
/RD（Chapter 14）
19
Table 8-1: Port 3 Alternate Functions
P3 Bit
Function
Pin
P3.0
RxD
10
P3.1
TxD
11
P3.2
INT0
12
P3.3
INT1
13
P3.4
T0
14
P3.5
T1
15
P3.6
WR
16
P3.7
RD
17

20
Table 8-2: RESET Value of Some 8051
Registers
Register
Reset Value
PC
0000
ACC
0000
B
0000
PSW
0000
SP
0007
DPTR
0000
RAM are all zero.

21
Figure 8-3 (a). Power-On RESET Circuit
Vcc
)|
+
10 uF
31
)|
30 pF
8.2 K
)|
30 pF
11.0592 MHz
19
18
EA/VPP
X1
X2
9 RST
RST
/EA
22
Figure 8-3 (b). Power-On RESET with
Debounce
Vcc
31
)|
10 uF
EA/VPP
X1
30 pF
X2
RST
)|
9
8.2 K

23
Figure 14-11 74LS373
PSEN
ALE
P0.0
P0.7
74LS373
G
D
Page 422
/OE: output Enable
/CE: chip enable
Page 426
Fig14-8 G: Enable
OE
CE
A0
A7
D0
D7
EA
P2.0
A8
P2.7
A15
8051
ROM
/PSEN
ALE: 24
next page
Reading ROM (1/2)
1. Send address
to ROM
PSEN
ALE High
P0.0
2. 74373 latches
the address and
send to ROM
74LS373
G
OE
CE
A0
D
P0.7
A7
Address
D0
D7
EA
P2.0
A8
P2.7
A15
25
8051
ROM
Reading ROM (2/2)
PSEN
ALE Low
P0.0
2. 74373 latches the address
and send to ROM
74LS373
G
OE
CE
A0
D
P0.7
A7
Address
D0
D7
EA
3. ROM send the instruction back
P2.0
A8
P2.7
A15
8051
ROM
ALE 26
Section 8.2
Design and Test of DS89C4x0 Trainer
27
Figure 8-5. Minimum Connection for
89C51/52-Based Systems
28
Figure 8-6. DS89C4x0 Trainer (for MAX232
connection, see Section 10.2)
29
Figure 8-7. Screen Capture from
HyperTerminal for DS89C4x0 Trainer
30
Table 8-3. Clocks per Machine Cycle
(MC) for Various 8051 Versions
31
Table 8-4. On-Chip Flash ROM Size for the
DS89C4x0 Family from Maxim-Dallas
Semiconductor. See www.maxim-ic.com
32
Section 8.3
Explaining the Intel Hex File
33
Intel Hex File
• Intel hex file is a file format designed to standardize
the loading of executable machine code.
– Loaders in every ROM burners support Intel hex file
format.
– The loader use the Intel hex file to download the opcode
into ROM.
– In DOS-based PC, you need a utility called OH (object-tohex) to produce Intel hex file format.
• The process of writing a 8051 program
*.asm  *.obj  *.abs  Intel hex file  ROM
editor assembler
linker
OH
loader
34
Figure 8-8. List file for Test Program
35
Figure 8-9. Intel Hex File Test Program
FF
36
Syntax in Figure 8-9.
• “:” Each line starts with a colom
• CC is the count of byte in this line.
– CC can range from 00 to 10H
• AAAA is for the 16-bit address.
• TT is for type.
– TT=00 : more line to come after this line
– TT=01 : last line.
• D is data (or code).
• SS is a single byte of checksum. See Example 8-4
37
Example 8-3
From Figure 8-9, analyze the six parts of line 3.
Solution:
:07 0020 00 DBFEDCFADDF62235
07: seven bytes of data
0020: the address of first byte in this line
00: not last line
DB FE DC FA DD F6 22: data (lines 17-20)
35: checksum
38
Example 8-4
(a) Verify the checksum byte for line 3 of Figure 8-9.
(b) Verify also the information is not corrupted.
Solution:
:07 0020 00 DBFEDCFADDF62235
(a) The sum is
=07+00+20+00+DB+FE+DC+FA+DD+F6+22=5CBH
The carry is dropped and
checksum=100H-CBH=35H
(b) Verify the information
07+00+20+00+DB+FE+DC+FA+DD+F6+22+35H
=600H
The carry is dropped and the result = 00H
39
Example 8-5
Compare the data portion of the Intel hex file of Figure 8-9 with the
opcodes in the list file of the test program given in Figure 8-8.
Do they match?
Solution:
In the first line of Figure 8-9, the data
portion starts with 75H, the opcode for the
instruction “MOV”, as shown in the list
file of Figure 8-8.
The last byte of the data in line3 of Figure
8-9 is 22, which is the opcode for the “RET”
in the list file of Figure 8-8.
40
You are able to (1/2)
• Explain the purpose of each pin of the 8051
microcontroller
• Show the hardware connection of the 8051 chip
• Explain how to design an 8051-based system
• Show the design of the DS89C4x0 Trainer
• Code the test program in Assembly and C for
testing the DS89C4x0
• Show how to delete programs for DS89C4x0 flash
ROM using PC HyperTerminal
41
You are able to (2/2)
• Show how to download programs into a
DS89C4x0 system using PC HyperTerminal
• Explain the Intel hex file
42