AT89C51RC Atmel Corporation, AT89C51RC Datasheet - Page 21

• Manufacturer Part Number: AT89C51RC
• Manufacturer: Atmel Corporation

Specifications of AT89C51RC

• Flash (kbytes): 32 Kbytes
• Max. Operating Frequency: 24 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Uart: 1
• Sram (kbytes): 0.5
• Operating Voltage (vcc): 4.0 to 6.0
• Timers: 3
• Watchdog: Yes

20. Program Memory Lock Bits
21. Programming the Flash
1920D–MICRO–6/08
The AT89C51RC has three lock bits that can be left unprogrammed (U) or can be programmed
(P) to obtain the additional features listed in
Table 20-1.
When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset.
If the device is powered up without a reset, the latch initializes to a random value and holds that
value until reset is activated. The latched value of EA must agree with the current logic level at
that pin in order for the device to function properly.
The AT89C51RC is shipped with the on-chip Flash memory array ready to be programmed. The
programming interface needs a high-voltage (12-volt) program enable signal and is compatible
with conventional third-party Flash or EPROM programmers.
The AT89C51RC code memory array is programmed byte-by-byte.
Programming Algorithm: Before programming the AT89C51RC, the address, data, and con-
trol signals should be set up according to
AT89C51RC, take the following steps:
1. Input the desired memory location on the address lines.
2. Input the appropriate data byte on the data lines.
3. Activate the correct combination of control signals.
4. Raise EA/V
5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The byte-
1
2
3
4
write cycle is self-timed and typically takes no more than 50 µs. Repeat steps 1
through 5, changing the address and data for the entire array or until the end of the
object file is reached.
Program Lock Bits
LB1
U
P
P
P
Lock Bit Protection Modes
PP
to 12V.
LB2
U
U
P
P
LB3
U
U
U
P
Protection Type
No program lock features
MOVC instructions executed from external program memory
are disabled from fetching code bytes from internal memory,
EA is sampled and latched on reset, and further
programming of the Flash memory is disabled
Same as mode 2, but verify is also disabled
Same as mode 3, but external execution is also disabled
Table 22-1
Table
20-1.
and Figures 22-1 and 22-2. To program the
AT89C51RC
21