HT24LC32
·
Write protect
·
Random read
The HT24LC32 can be used as a serial ROM when
the WP pin is connected to VCC . Programming will be
in h i bi t e d and t he e n ti r e m e m o r y w i ll b e
write-protected.
·
Read operations
Read operations are initiated in the same way as write
operations with the exception that the read/write se-
lect bit in the device address word is set to one. There
are three read operations: current address read, ran-
dom address read and sequential read.
·
Current address read
A random read requires a dummy byte write sequence
to load in the data word address which is then clocked
in and acknowledged by the EEPROM. The
microcontroller must then generate another start con-
dition. The microcontroller now initiates a current ad-
dress read by sending a device address with the
read/write select bit high. The EEPROM acknowl-
edges the device address and serially clocks out the
data word. The microcontroller should respond with a
²no
ACK² signal (high) followed by a stop condition
(refer to Random read timing).
·
Sequential read
The internal data word address counter maintains the
last address accessed during the last read or write op-
eration, incremented by one. This address remains
valid between operations as long as the chip power is
maintained. The address will roll over during read
from the last byte of the last memory page to the first
byte of the first page. The address will roll over during
write from the last byte of the current page to the first
byte of the same page. Once the device address with
the read/write select bit set to one is clocked in and ac-
knowledged by the EEPROM, the current address
data word is serially clocked out. The microcontroller
does not respond with an input zero but generates a
following stop condition (refer to Current read timing).
R e a d
S ta rt
S D A L in e
W r ite
Sequential reads are initiated by either a current ad-
dress read or a random address read. After the
microcontroller receives a data word, it responds with
an acknowledgment. As long as the EEPROM re-
ceives an acknowledgment, it will continue to incre-
ment the data word address and serially clock out
sequential data words. When the memory address
limit is reached, the data word address will roll over
and the sequential read continues. The sequential
read operation is terminated when the microcontroller
does not respond with a zero but generates a following
stop condition.
S to p
D e v ic e a d d r e s s
A 2 A 1 A 0
D a ta
Current Address Read Timing
A C K
R /W
N o A C K
R e a d
D e v ic e A d d r e s s
A 2 A 1 A 0
1 s t, 2 n d W o rd
A d d re s s (n )
S ta rt
S D A L in e
S ta rt
S to p
D e v ic e A d d r e s s
A 2 A 1 A 0
D a ta (n )
D u m m y W r ite
N o t e : * = D o n 't c a r e b it s
A C K
R /W
Random Read Timing
A C K
A C K
N o A C K
R e a d
D e v ic e
A d d re s s
S D A L in e
S to p
D a ta (n )
D a ta (n + 1 )
D a ta (n + 2 )
D a ta (n + x )
A C K
R /W
A C K
A C K
N o A C K
Sequential Read Timing
A C K
Rev. 1.00
5
March 16, 2006
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
