HT45R22E Holtek Semiconductor, HT45R22E Datasheet - Page 20

• Manufacturer Part Number: HT45R22E
• Description: Remote Type 8-bit OTP MCU
• Manufacturer: Holtek Semiconductor

Rev. 1.00
Acknowledge polling
To maximize bus throughput, one technique is to allow
the master to poll for an acknowledge signal after the
start condition and the control byte for a write com-
mand have been sent. If the device is still busy imple-
menting its write cycle, then no ACK will be returned.
The master can send the next read/write command
when the ACK signal has finally been received.
Write protect
The EEPROM has a write-protect function and pro-
gramming will then be inhibited when the WP pin is
connected to V
used as a serial ROM.
Read operations
The EEPROM supports three read operations,
namely, current address read, random address read
and sequential read. During read operation execution,
the read/write select bit should be set to 1 .
Acknowledge Polling Flow
DD
. Under this mode, the EEPROM is
Sequential Read Timing
Random Read Timing
Current Read Timing
20
Current address 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 stays valid
between operations as long as the chip power is main-
tained. The address roll over during read from the last
byte of the last memory page to the first byte of the first
page. The address 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 se-
lect bit set to one is clocked in and acknowledged by
the EEPROM, the current address data word is seri-
ally clocked out. The microcontroller should respond
with a no ACK signal (high) followed by a stop condi-
tion (refer to Current read timing).
Random 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
(refer to Random read timing).
Sequential read
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
responds with a no ACK signal (high) followed by a
stop condition.
no ACK signal (high) followed by a stop condition
HT45R22E
March 17, 2010
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