22
AT89C51RC
1920B–MICRO–11/02
Programming the
Flash
The AT89C51RC is shipped with the on-chip Flash memory array ready to be pro-
grammed. 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 control signals should be set up according to the Flash programming mode table
and Figures 10 and 11. To program the 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
PP
to 12V.
5. Pulse ALE/PROG once to program a byte in the Flash array or the lock bits. The
byte-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.
Chip Erase Sequence: Before the AT89C51RC can be reprogrammed, a Chip Erase
operation needs to be performed. To erase the contents of the AT89C51RC, follow this
sequence:
1. Raise V
CC
to 6.5V.
2. Pulse ALE/PROG once (duration of 200 ns - 500 ns) and wait for 150 ms.
3. Power V
CC
down and up to 6.5V.
4. Pulse ALE/PROG once (duration of 200 ns - 500 ns) and wait for 150 ms.
5. Power V
CC
down and up.
Data
Polling: The AT89C51RC features Data Polling to indicate the end of a write
cycle. During a write cycle, an attempted read of the last byte written will result in the
complement of the written data on P0.7. Once the write cycle has been completed, true
data is valid on all outputs, and the next cycle may begin. Data
Polling may begin any
time after a write cycle has been initiated.
Ready/Busy: The progress of byte programming can also be monitored by the
RDY/BSY
output signal. P3.0 is pulled low after ALE goes high during programming to
indicate BUSY
. P3.0 is pulled high again when programming is done to indicate READY.
Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed
code data can be read back via the address and data lines for verification. The status of
the individual lock bits can be verified directly by reading them back.
Reading the Signature Bytes: The signature bytes are read by the same procedure as
a normal verification of locations 000H, 100H, and 200H, except that P3.6 and P3.7
must be pulled to a logic low. The values returned are as follows:
(000H) = 1EH indicates manufactured by Atmel
(100H) = 51H
(200H) = 07H indicates 89C51RC
