Eprom Programming Sequence - Motorola MC68HC05T16 Technical Data Manual

ELAT - EPROM Latch Control
1 (set) – EPROM address and data bus configured for programming (writes to
EPROM cause address data to be latched). EPROM is in
programming mode and cannot be read if ELAT is 1. This bit should
not be set unless a programming voltage is applied to the V
0 (clear) – EPROM address and data bus configured for normal reads.
PGM - EPROM Program Command
1 (set) – Programming power connected to the EPROM array. If ELAT not = 1
then PGM = 0.
0 (clear) – Programming power disconnected from the EPROM array.
13.3.3

EPROM Programming Sequence

Programming the EPROM of the MC68HC705T16 is as follows:
1) Set the ELAT bit.
2) Write the data to be programmed to the address to be programmed.
3) Set the PGM bit.
4) Delay for the appropriate amount of time.
5) Clear the PGM and the ELAT bits.
The last action may be carried out in a single CPU write operation. It is important to remember
that an external programming voltage must be applied to the V
should be equal to V
DD
Example shows address $B000 is programmed with $00.
CLR PCR
LDX #$00
BSET 1,PCR
LDA #$00
STA $B000,X
BSET 0,PCR
JSR DELAY
CLR PCR
MC68HC05T16
during normal operation.
;reset PCR
;load index register with 00
;set ELAT bit
;load data=00 in to A
;latch data and address (if programming OSD CHAR
;EPROM, the address should be in the range of
;$8000 to $8FFF)
;program
;call delay subroutine for 1ms
;reset PCR
OPERATING MODES
pin.
PP
pin while programming, but
PP
MOTOROLA
13
TPG
13-5