NEC PD750008 - Manual (Page 252)

232
µPD75008 USER'S MANUAL
9.3 READING THE PROGRAM MEMORY
The procedure for reading the contents of program memory is described below. The read is performed
in the verify mode.
(1) Pull low all unused pins to V
SS
by means of resistors. Bring X1 to low level.
(2) Apply 5 V to V
DD
and V
PP
.
(3) Wait 10 µs.
(4) Select program memory address clear mode.
(5) Apply 6 V to V
DD
and 12.5 V to V
PP
.
(6) Select program inhibit mode.
(7) Select verify mode. Data is output sequentially one address at a time for each cycle of four clock pulses
appearing on the X1 pin.
(8) Select program inhibit mode.
(9) Select program memory address clear mode.
(10) Apply 5 V to V
DD
and to V
PP
.
(11) Turn the power off.
The timing for steps (2) to (9) is shown below.
V PP
V
DD
V PP
V
DD+1
V DD
V DD
X1
P40-P43
P50-P53
MD0
(P30)
MD1
(P31)
MD2
(P32)
MD3
(P33)
Data output Data output
“L”