ht82m9aae Holtek Semiconductor Inc., ht82m9aae Datasheet - Page 19

• Manufacturer Part Number: ht82m9aae
• Description: Usb Mouse Encoder 8-bit Mcu With Eeprom
• Manufacturer: Holtek Semiconductor Inc.

Write Operations
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Rev. 1.20
Byte write
A write operation requires an 8-bit data word address
following the device address word and acknowledg-
ment. Upon receipt of this address, the EEPROM will
again respond with a zero and then clock in the first
8-bit data word. After receiving the 8-bit data word, the
EEPROM will output a zero and the addressing de-
vice, such as a microcontroller, must terminate the
write sequence with a stop condition. At this time the
EEPROM enters an internally-timed write cycle to the
non-volatile memory. All inputs are disabled during
this write cycle and EEPROM will not respond until the
write is completed (refer to Byte write timing).
Acknowledge polling
To maximise 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.
Acknowledge Polling Flow
Random Read Timing
Current Read Timing
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Read operations
The data 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 ²1².
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 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
should respond a No ACK (High) signal and following
stop condition (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
²no ACK² signal (high) followed by a stop condition.
(refer to Random read timing).
HT82M9AEE/HT82M9AAE
August 13, 2007