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4.5
Toggle Bit
In addition to DATA Polling, the AT28HC64BF provides another method for determining the end
of a write cycle. During the write operation, successive attempts to read data from the device will
result in I/O6 toggling between one and zero. Once the write has completed, I/O6 will stop tog-
gling, and valid data will be read. Toggle bit reading may begin at any time during the write cycle.
4.6
4.6.1
4.6.2
4.7
4
Data Protection
If precautions are not taken, inadvertent writes may occur during transitions of the host system
power supply. Atmel ? has incorporated both hardware and software features that will protect the
memory against inadvertent writes.
Hardware Protection
Hardware features protect against inadvertent writes to the AT28HC64BF in the following ways:
(a) V CC sense – if V CC is below 3.8 V (typical), the write function is inhibited; (b) V CC power-on
delay – once V CC has reached 3.8 V, the device will automatically time out 5 ms (typical) before
allowing a write; (c) write inhibit – holding any one of OE low, CE high or WE high inhibits write
cycles; and (d) noise filter – pulses of less than 15 ns (typical) on the WE or CE inputs will not ini-
tiate a write cycle.
Software Data Protection
A software-controlled data protection feature has been implemented on the AT28HC64BF.
When enabled, the software data protection (SDP), will prevent inadvertent writes. The SDP fea-
ture may be enabled or disabled by the user; the AT28HC64BF is shipped from Atmel with SDP
disabled.
SDP is enabled by the user issuing a series of three write commands in which three specific
bytes of data are written to three specific addresses (refer to the “Software Data Protection Algo-
rithm” diagram on page 10 ). After writing the 3-byte command sequence and waiting t WC , the
entire AT28HC64BF will be protected against inadvertent writes. It should be noted that even
after SDP is enabled, the user may still perform a byte or page write to the AT28HC64BF. This is
done by preceding the data to be written by the same 3-byte command sequence used to enable
SDP.
Once set, SDP remains active unless the disable command sequence is issued. Power transi-
tions do not disable SDP, and SDP protects the AT28HC64BF during power-up and power-
down conditions. All command sequences must conform to the page write timing specifications.
The data in the enable and disable command sequences is not actually written into the device;
their addresses may still be written with user data in either a byte or page write operation.
After setting SDP, any attempt to write to the device without the 3-byte command sequence will
start the internal write timers. No data will be written to the device, however. For the duration of
t WC , read operations will effectively be polling operations.
Device Identification
An extra 64 bytes of EEPROM memory are available to the user for device identification. By rais-
ing A9 to 12 V ± 0.5 V and using address locations 1FC0H to 1FFFH, the additional bytes may
be written to or read from in the same manner as the regular memory array.
AT28HC64BF
3648B–PEEPR–4/09
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相关代理商/技术参数
AT28HC64BF-12JU SL383
制造商:Atmel Corporation 功能描述:EEPROM Parallel 64K-Bit 8K x 8 5V 32-Pin PLCC T/R 制造商:Atmel Corporation 功能描述:, 1M (128K X 8), 5V, SDP - 120NS, PLCC, IND TEMP, GREEN PKG - Tape and Reel
AT28HC64BF-12JU-T
功能描述:IC EEPROM 64KBIT 120NS 32PLCC 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:在售 存储器类型:非易失 存储器格式:EEPROM 技术:EEPROM 存储容量:64Kb （8K x 8） 写周期时间 - 字，页:10ms 访问时间:120ns 存储器接口:并联 电压 - 电源:4.5 V ~ 5.5 V 工作温度:-40°C ~ 85°C（TC） 安装类型:表面贴装 封装/外壳:32-LCC（J 形引线） 供应商器件封装:32-PLCC（11.43x13.97） 标准包装:1
AT28HC64BF-12PU
功能描述:电可擦除可编程只读存储器 1M 5V SDP - 120NS IND TEMP RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8
AT28HC64BF-12SU
功能描述:电可擦除可编程只读存储器 1M 5V SDP - 120NS IND TEMP RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8
AT28HC64BF-12SU SL383
制造商:Atmel Corporation 功能描述:PARALLEL EEPROM, 64K (8K X 8), 制造商:Atmel Corporation 功能描述:EEPROM PARALLEL 64KBIT 8KX8 5V 28SOIC W - Tape and Reel
AT28HC64BF-12SU-T
功能描述:120NS, SOIC, IND TEMP, GREEN 制造商:microchip technology 系列:- 包装:剪切带（CT） 零件状态:在售 存储器类型:非易失 存储器格式:EEPROM 技术:EEPROM 存储容量:64Kb （8K x 8） 写周期时间 - 字，页:10ms 访问时间:120ns 存储器接口:并联 电压 - 电源:4.5 V ~ 5.5 V 工作温度:-40°C ~ 85°C（TC） 安装类型:表面贴装 封装/外壳:28-SOIC（0.295"，7.50mm 宽） 供应商器件封装:28-SOIC 标准包装:1
AT28HC64BF-12TU
功能描述:电可擦除可编程只读存储器 1M 5V SDP - 120NS IND TEMP RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8
AT28HC64BF-70JU
功能描述:电可擦除可编程只读存储器 1M 5V SDP - 70NS IND TEMP RoHS:否 制造商:Atmel 存储容量:2 Kbit 组织:256 B x 8 数据保留:100 yr 最大时钟频率:1000 KHz 最大工作电流:6 uA 工作电源电压:1.7 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8