External Bus Interface
C513AO
User’s Manual
4-7
05.99
4.5.2 Protected ROM/OTP Mode
For the C513AO-2R ROM protected by mask, and for the C513AO-2E OTP in Protection Level 1,
ROM/OTP Verification Mode 2, shown in Figure 4-4, is used to verify the content of the ROM/OTP.
The detailed timing characteristics of the ROM/OTP verification mode are shown in the data sheet.
Figure 4-4
ROM Verification Mode 2
ROM/OTP Verification Mode 2 is selected if the inputs PSEN, EA, and ALE are set to the specified
logic levels. With RESET going inactive, the ROM/OTP Verification Mode 2 sequence is started.
The C513AO outputs an ALE signal with a period of 12
t
CLCL
and expects data bytes at Port 0. The
data bytes at Port 0 are assigned to the ROM addresses in the following way:
1. Data Byte =
content of internal ROM/OTP address 0000H
2. Data Byte =
content of internal ROM/OTP address 0001H
3. Data Byte =
content of internal ROM/OTP address 0002H
:
16. Data Byte =
content of internal ROM/OTP address 000FH
:
The C513AO does not output any address information during ROM/OTP Verification Mode 2. The
first data byte to be verified is always the byte which is assigned to the internal ROM address 0000H
and must be put onto the data bus with the falling edge of RESET. With each following ALE pulse,
the ROM/OTP address pointer is internally incremented and the expected data byte for the next
ROM address must be delivered externally.
The data at Port 0 is latched between two ALE pulses, (at 6
t
CLCL
after ALE rising edge) and is
compared internally with the ROM/OTP content of the actual address. If a verify error is detected,
the error condition is stored internally. After each 16th data byte the cumulated verify result (pass
Data for
Addr. 0
Data for
Addr. 1
Data for
Addr. 2
MCD04197
RESET
ALE
Port 0
P3.5
12
t
CLCL
6
t
CLCL
1st ALE pulse
after RESET
Latch
Latch
Latch
Latch
Latch
Inputs: ALE =
V
SS
PSEN =
V
IH
RESET =
EH =
V
IH2
Data for
Addr. X 16+1
*
Data for
Addr. X 16
*
Data for Ad.
X 16-1
*
Verify Result for previous
16 bytes of data:
Low: Verify Error
High: Verify OK
