Intel mcs-48 manual Crystal Oscillator Mode, LC Oscillator Mode, Driving from External Source

8048/8035L/8748/8748-6/8748-8/8035/8035-8

CRYSTAL OSCILLATOR MODE

C1
	f--""T--...		,.---=-t2 XTAL 1
~C2		I	HIMHz
		...._--1i-___...	.'------. I
.....		I
		I

r--~--~--~ XTAL2

C3

C2. 5pF + 1f2pF + STRAY 6pF

C2 • CRYSTAL + STRAY 8pF

C3. 20pF + 1pF + STRAY 6pF

CRYSTALSERIES RESISTANCE SHOULO BE LESS THAN 7& AT 8MHz: LESS THAN 180 AT S.BMHz.

LC OSCILLATOR MODE

.l.	.£.	~
. 45"H	20 pF	5.2 MHz
120"H	20pF	3.2 MHZ.....-_.__-"'l2XTAL1

L - _....._~3XTAL2	c•• = 5 -10 pF PIN·TO·PIN
	CAPACITANCE

EACH C SHOULD BE APPROXIMATELY 20 pF, INCLUDING STRAY CAPACITANCE.

DRIVING FROM EXTERNAL SOURCE

+SV

47012

10-+-____2=-1XTAL1

+5V

470Q

3

L - _....._....:"'XTAL2

FOR XTAL 1 ANDXTAL2DEFINE"HIGH" ASVOLTAGESABOVE 1.8VAND "LOW" AS VOLTAGES BELOW 1.8V. THE DUTY CYCLE REQUIREMENTS FOR EXTER- NALLY DRIVING XTAL 1 AND XTAL 2 USING THE CIRCUIT SHOWN ABOVE ARE AS FOLLOWS:

FOR THE 8046, XTAL 1 MUST BE HIGH 35-85'110OF THE PERIOD AND XTAL 2

MUST BE HIGH 36-85'110OF THE PERIOD.

. FOR THE 8748. XTAL MUST BE HIGH 48-t10'II0OFTHE PERIOD AND XTAL 2 MUST BE HIGH 50-65'110OF THE PERIOD.

RISE AND FALL TIMES MUST NOT EXCEED IOn••

PROGRAMMING, VERIFYING, AND ERASING THE 8748 EPROM

Programming Verification

In brief, the programming process consists of: activat· ing the program mode, applying an address, latching the address, applying data, and applying a programming pulse. Each word is programmed compietely before moving on to the next and is followed by a verification step. The following is a list of the pins used for program- ming and a description of their functions:

Pin	Function
XTAL1	Clock Input (1 to 6 MHz)
AESET	Initialization and Address Latching
TEST 0	Selection of Program or Verify Mode
EA	Activation of ProgramlVerify Modes
BUS	Address and Data Input
	Data Output during Verify
P20-1	Address Input
Voo	Programming Power Supply
PAOG	Program Puise Input

WARNING:

An attempt to program a mis-socketed 8748 wlil result In severe damage to the part. An indication of a properly socketed part is the appearance of the ALE clock out- put. The lack of this clock may be used to disable the programmer.

The ProgramlVerify Sequence Is:

1.Voo = SV, clock applied or internal oscillator oper- ating, AESET=OV, TEST O=SV, EA=SV, BUS and PAOG fioating.

2.Insert 8748 in programming socket.

3.TEST 0 = OV (select program mode).

4.EA = 23V (activate program mode), S. Address applied to BUS and P20-1.

6.AESET = SV (latch address).

7.Data applied to BUS.

8.Voo = 2SV (programming power).

9.PAOG = OV followed by one SO ms pulse to 23 V.

10.Voo=SV.

11.TEST 0 = SV (verify mode).

12.Read and verify data on BUS.

13.TEST O=OV.

14.FiES'E'f= OV and repeat from step S.

1S. Programmer should be at conditions of step 1 when 8748 is removed from socket.

6-1S AFN..Q1364A..Q7