at89c55-16qa ATMEL Corporation, at89c55-16qa Datasheet - Page 14

• Manufacturer Part Number: at89c55-16qa
• Description: 8-bit Microcontroller With Bytes Flash
• Manufacturer: ATMEL Corporation

Data Polling: The AT89C55 features Data Polling to indi-
cate the end of a write cycle. During a write cycle, an
attempted read of the last byte written will result in the com-
plement of the written data on PO.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. P3.4 is pulled
low after ALE goes high during programming to indicate
BUSY. P3.4 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 lock bits
cannot be verified directly. Verification of the lock bits is
achieved by observing that their features are enabled.
Chip Erase: The entire Flash array is erased electrically
by using the proper combination of control signals and by
holding ALE/PROG low for 10 ms. The code array is written
with all 1s. The chip erase operation must be executed
before the code memory can be reprogrammed.
Figure 9. Programming the Flash Memory
*Programming address line A14 (P3.0) is not the same as the external
4-182
memory address line A14 (P2.6)
PROGRAMMING
MODES TABLE
SEE FLASH
3-33 MHz
0000H/4FFFH
ADDR.
A0 - A7
A8 - A13
A14*
AT89C55
P1
P2.0 - P2.5
P3.0
P2.6
P2.7
P3.6
P3.7
XTAL2
XTAL 1
GND
AT89C55
PSEN
RST
ALE
V
EA
P0
CC
+5V
PGM
DATA
PROG
V /V
V
I H
I H
PP
Reading the Signature Bytes: The signature bytes are
read by the same procedure as a normal verification of
locations 030H, 031H, and 032H, except that P3.6 and
P3.7 must be pulled to a logic low. The values returned are
as follows.
Programming Interface
Every code byte in the Flash array can be written, and the
entire array can be erased, by using the appropriate combi-
nation of control signals. The write operation cycle is self-
timed and once initiated, will automatically time itself to
completion.
All major programming vendors offer worldwide support for
the Atmel microcontroller series. Please contact your local
programming vendor for the appropriate software revision.
Figure 10. Verifying the Flash Memory
PROGRAMMING
MODES TABLE
3-33 MHz
SEE FLASH
(030H) = 1EH indicates manufactured by Atmel
(031H) = 55H indicates 89C55
(032H) = FFH indicates 12V programming
(032H) = 05H indicates 5V programming
0000H/4FFFH
ADDR.
A8 - A13
A14*
A0 - A7
P1
P2.0 - P2.5
P2.6
P2.7
P3.6
P3.7
XTAL 2
XTAL 1
GND
P3.0
AT89C55
PSEN
RST
ALE
V
EA
P0
CC
+5V
PGM DATA
(USE 10K
PULLUPS)
V
V
I H
I H