GMS90 Series
encryption table is disabled. However, the other security bit can still be programmed. Note that the EA/VPP pin
must not be allowed to go above the maximum specified VPP level for any amount of time. Even a narrow glitch
above that voltage can cause permanent damage to the device. The VPP source should be well regulated and free
glitches and overshoot.
+5V
V
CC
P1
A0-A7
PROGRAM DATA
+12.75V
P0
P2.0
-P2.5
A8-A13
EA/V
PP
P3.4
A14
1
1
1
RST
P3.6
P3.7
☞NOTE
ALE/PROG
0
1
PSEN
P2.7
XTAL2
XTAL1
4~6MHz
P2.6
1
V
SS
NOTE:
GMS97X51/52:
100µs × 25 pulses to GND
GMS97X54/56/58: 100µs × 10 pulses to GND
Figure 12. Programming Configuration
Program Verification
If security bit 2 has not been programmed, the on-chip program memory can be read out for program verifica-
tion. The address of the program memory location to be read is applied to ports 1 and 2 as shown in Figure 15.
The other pins are held at the "Verify Code Data" levels indicated in Table 11. The contents of the address lo-
cation will be emitted on port 0 for this operation. If the encryption table has been programmed, the data pre-
sented at port 0 will be the exclusive NOR of the program byte with one of the encryption bytes. The user will
have to know the encryption table contents in order to correctly decode the verification data. The encryption
table itself cannot be read out.
48
Dec. 1998 Ver 3.0
HYNIX [ HYNIX SEMICONDUCTOR ]
