fm3316 Ramtron Corporation, fm3316 Datasheet - Page 20

• Manufacturer Part Number: fm3316
• Description: 3v Integrated Processor Companion With Memory
• Manufacturer: Ramtron Corporation

RDSR – Read Status Register
The RDSR command allows the bus master to verify
the contents of the Status Register. Reading this
register provides information about the current state
of the write protection bits. Following the RDSR op-
code, the FM33xx will return one byte with the
contents of the Status Register. The Status Register is
described in detail in a later section.
RDPC – Read Processor Companion
The RDPC command allows the bus master to verify
the contents of the Processor Companion registers.
Following the RDPC op-code, a single-byte register
address is sent. The FM33xx will then return one or
more bytes with the contents of the companion
registers. When reading multiple data bytes, the
internal register address will wrap around to 00h
after 1Dh is reached.
Rev. 1.1
Dec. 2007
SCK
CS
SO
SI
0
0
0
1
0
2
o p - c od e
1
3
Hi-Z
0
4
0
5
1
6
Figure 17. Processor Companion Read
Figure 16. WRSR Bus Configuration
Figure 15. RDSR Bus Configuration
1
7
MSB
7
0
6
1
Register Address
5
2
4
3
3
4
5
2
WRPC – Write Processor Companion
The WRPC command is used to set companion
control settings. A WREN command is required
prior to sending the WRPC command. Following the
WRPC op-code, a single-byte register address is
sent. The controller then drives one or more bytes to
program the companion registers. When writing
multiple data bytes, the internal register address will
wrap around to 00h after 1Dh is reached. The rising
edge of /CS terminates a WRPC operation. See
Figure 18.
WRSR – Write Status Register
The WRSR command allows the user to select
certain write protection features by writing a byte to
the Status Register. Prior to sending the WRSR
command, the user must send a WREN command to
enable writes. Note that executing a WRSR
command is a write operation and therefore clears
the Write Enable Latch. The bus timings of RDSR
and WRSR are shown below.
6
1
LSB
0
7
FM33256/FM3316 SPI Companion w/ FRAM
MSB
7
0
6
1
5
2
4
3
Data Out
3
4
5
2
6
1
LSB
7
0
LSB
7
0
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