MC68HC05T16
MOTOROLA
13-5
OPERATING MODES
13
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
PP
pin.
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
PP
pin while programming, but
should be equal to V
DD
during normal operation.
Example shows address $B000 is programmed with $00.
CLR
PCR
;reset PCR
LDX
#$00
;load index register with 00
BSET
1,PCR
;set ELAT bit
LDA
#$00
;load data = 00 in to A
STA
$B000,X
;latch data and address (if programming OSD CHAR
;EPROM, the address should be in the range of
;$8000 to $8FFF)
BSET
0,PCR
;program
JSR
DELAY
;call delay subroutine for 1ms
CLR
PCR
;reset PCR
TPG
113
Summary of Contents for MC68HC05T16
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