Intel mcs-48 manual Programming, Verifying and Erasing Eprom, Reset

		SINGLE COMPONENT SYSTEM
	Pin
Designation	Number	Function
RESET	4	Input which is used to initialize the processor. Also used
		during PROM programming and verification. (Active low)
		(Internal pullup "'"200KO)
WR	10	Output strobe during a BUS write. (Active low)
		Used as write strobe to external data memory.
ALE	11	Address Latch Enable. This signal occurs once during
		each cycle and is useful as a clock output.

The negative edge of ALE strobes address into external data and program memory.

9Program Store Enable. This output occurs only during a fetch to external program memory. (Active Low)

5Single step input can be used in conjunction with ALE to "single step" the processor through each instruction.

(Active Low) (Internal pullup '"300KOl

EA	7	External Access input which forces all program memory
		fetches to reference external memory. Useful for emula-
		tion and debug, and essential for testing and program
		verification. (Active High)	(Internal pullup '"10MO
		on 8048/8049, 8035L, 8039 only)
XTAL1	2	One side of crystal input for internal oscillator. Also input
		for external source.
XTAL2	3	Other side of crystal/external source input.

Unless otherwise stated inputs do not have internal pullup resistors.

2.3Programming, Verifying and Erasing EPROM

The internal Program Memory of the 8748 may be erased and reprogrammed by the user as explained in the following sections. See also the 8748 data sheet.

2.3.1 ProgramminglVerification

In brief, the programmin'gprocess consists of: activating the program mode, applying an address, latching the address, applying data, and applying a programming pulse. Each word is programmed completely before moving on to the next and is followed .by a verifica- tion step. The following is a list of the pins used for programming and a description of their functions:

Pin	Function
XTAL 1	Clock Input (1 to 6MHz)
Reset	Initialization and Address
	Latching
Test 0	Selection of Program (OV) or
	Verify (5V) Mode
EA	Activation of Program/Verify
	Modes
BUS	Address and Data Input
	Data Output During Verify
P2D-1	Address Input
Voo	Programming Power Supply
PROG	Program Pulse Input

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