Intel mcs-48 manual Reading Internal Program Memory

SINGLE COMPONENT SYSTEM

The processor is placed in the READ mode by applying a high voltage (+23V for the 8748, +12V for the 8048/8049) to the EA pin and +5V to the TO (8748 only) input pin. RESET must. be at OV when voltage is ap- plied to EA. The address of the location to be read is then applied to the same lines (TTL levels) of BUS and Port 2 which output

the address during single step (see below). The address is latched by a "0" to "1" transition on RESET and a high level on RESET causes the contents of the program memory location addressed to appear on the eight lines of BUS. RESET must be brought back to OV before leaving the READ mode.

P22

P21

P20

DB7

DB8

DBS

DB4

804B

B748

DB3

DB2

OBI

DBO

RESET

EA I ---

ALE TO l-

TO

8748 ONLY

5V

RESET

+12V (+23V)

EA

5V

BUS

5V

P2[J.21

A1D (8049) only)

		A,
		Aa
	I. I	---- A7
liD.	I'i -- Aa
	I, i -- As
1/0,	10 I---- A4			-
6218 D . r - D,
110,	0, 1 ---- 00
	0,1 ---- 0•
1100	00 r - D,
i5iE'N	a-
f	~			r- DATA OUT
	O,r - D•
1/0.	O'r - Do
	0,1 ---- 0 ,			-
1/0,	001 ---- 0 0
8218	I . i -- A•
1/0,	I,t --- A,
	I'I ---- A,
1/00	lot --- Ao			I
i5iEN	Ci
t	~				1/2
				Q	7474 0	RESET'
		-[+23V	8748	I	CK
		+12V	8048		J
		{+5V	8748
		NC	8048

L -

I

i

I

I

< ADDRESS >< DATA

<ADDRESS

READING INTERNAL PROGRAM MEMORY

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