25LC320
2.2
Read Status Register (RDSR)
2.0
PRINCIPLES OF OPERATION
The 25LC320 is a 4096 byte EEPROM designed to
interface directly with the serial peripheral interface
(SPI ) port of many of today’s popular microcontroller
families, including Microchip’s midrange PIC16CXX
microcontrollers. It may also interface with microcontrol-
lers that do not have a built-in SPI port by using dis-
crete I/O lines programmed properly with software.
The RDSR instruction provides access to the status
register. The status register may be read at any time,
even during a write cycle. The status register is format-
ted as follows:
7
6
5
4
3
2
1
0
WPEN
X
X
X
BP1
BP0
WEL
WIP
The Write-In-Process (WIP) bit indicates whether the
25LC320 is busy with a write operation. When set to a
‘1’ a write is in progress, when set to a ‘0’ no write is in
progress. This bit is read only.
The 25LC320 contains an 8-bit instruction register.The
part is accessed via the SI pin, with data being clocked
in on the rising edge of SCK. If the WPEN bit in the Sta-
tus Register is set, the WP pin must be held high to
allow writing to the non-volatile bits in the status regis-
ter.
The Write Enable Latch (WEL) bit indicates the status
of the write enable latch. When set to a ‘1’ the latch
allows writes to the array and status register, when set
to a ‘0’ the latch prohibits writes to the array and status
register. The state of this bit can always be updated via
the WREN or WRDI commands regardless of the state
of write protection on the status register.This bit is read
only.
Table 2-1 contains a list of the possible instruction bytes
and format for device operation. All instructions,
addresses and data are transferred MSB first, LSB last.
Data is sampled on the first rising edge of SCK after CS
goes low. If the clock line is shared with other peripheral
devices on the SPI bus, the user can assert the
HOLD input and place the 25LC320 in ‘HOLD’ mode.
After releasing the HOLD pin, operation will resume
from the point when the HOLD was asserted.
The Block Protection (BP0 and BP1) bits indicate
which blocks are currently write protected. These bits
are set by the user issuing the WRSR instruction.
These bits are non-volatile.
2.1
Write Enable (WREN) and Write
Disable (WRDI)
The Write Protect Enable (WPEN) bit is a non-volatile
bit that is available as an enable bit for the WP pin. The
Write Protect (WP) pin and the Write Protect Enable
(WPEN) bit in the status register control the
programmable hardware write protect feature.
Hardware write protection is enabled when WP pin is
low and the WPEN bit is high. Hardware write
protection is disabled when either the WP pin is high or
the WPEN bit is low. When the chip is hardware write
protected, only writes to non-volatile bits in the status
register are disabled. See Table 2-2 for matrix of
functionality on the WPEN bit and Figure 2-1 for a
flowchart of Table 2-2. See Figure 3-5 for RDSR timing
sequence.
The 25LC320 contains a write enable latch. This latch
must be set before any write operation will be
completed internally. The WREN instruction will set the
latch, and the WRDI will reset the latch.The following is
a list of conditions under which the write enable latch
will be reset:
• Power-up
• WRDI instruction successfully executed
• WRSR instruction successfully executed
• WRITE instruction successfully executed
TABLE 2-1:
INSTRUCTION SET
Instruction Name Instruction Format
Description
WREN
WRDI
RDSR
WRSR
READ
WRITE
0000 0110
0000 0100
0000 0101
0000 0001
0000 0011
0000 0010
Set the write enable latch (enable write operations)
Reset the write enable latch (disable write operations)
Read status register
Write status register (write protect enable and block write protection bits)
Read data from memory array beginning at selected address
Write data to memory array beginning at selected address
TABLE 2-2:
WRITE PROTECT FUNCTIONALITY MATRIX
WPEN
WP
WEL
Protected Blocks
Unprotected Blocks
Status Register
0
0
1
1
X
X
X
X
Low
Low
High
High
0
1
0
1
0
1
Protected
Protected
Protected
Protected
Protected
Protected
Protected
Writable
Protected
Writable
Protected
Writable
Protected
Writable
Protected
Protected
Protected
Writable
1996 Microchip Technology Inc.
Preliminary
DS21158B-page 5
5秒后页面跳转
NTC热敏电阻与PTC热敏电阻的应用原理及应用范围
GTO与普通晶闸管相比为什么可以自关断？为什么普通晶闸管不能呢？从GTO原理、应用范围带你了解原因及推荐型号
LF353数据手册解读：特性、应用、封装、引脚说明、电气参数及替换型号推荐
A4950资料手册解读：特性、应用、封装、引脚功能、电气参数及代换型号
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
数据手册
如果您发现信息不准确，
