User’s Manual
4-8
05.99
External Bus Interface
C513AO
or fail) of the last 16 verify operations is output at P3.5. P3.5 is always set or cleared after each 16
byte block of the verify sequence. In ROM/OTP Verification Mode 2, the C513AO must be provided
with a system clock at the XTAL pins.
Figure 4-5 shows an application example of external circuitry used to verify a protected ROM/OTP
inside the C513AO in ROM/OTP Verification Mode 2. With RESET going inactive, the C513AO
starts the ROM/OTP verify sequence. Its ALE is clocking a 14-bit address counter. This counter
generates the addresses for an external EPROM which is programmed with the content of the
internal (protected) ROM/OTP. The verify detect logic typically displays the state of the verify error
output P3.5. P3.5 can be latched with the falling edge of ALE.
When the last byte of the internal ROM/OTP has been handled, the C513AO starts generating a
PSEN signal. This PSEN signal or the Carry (CY) signal of the address counter indicates, to the
verify detect logic, the end of the internal ROM/OTP verification.
Figure 4-5
ROM/OTP Verification Mode 2 - External Circuitry Example
MCB02595
Verify
Detect
Logic
&
&
DD
V
14-Bit
Address
Counter
CY
R
2 k
Ω
Compare
Code
ROM
A0-A13
CS
OE
D0-D7
P3.5
ALE
RESET
0
Port
C513AO
DD
V
EA
PSEN
CLK