Fujitsu FR81S User Manual
CHAPTER 45: FLASH MEMORY
4. Registers
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : FLASH MEMORY
FUJITSU SEMICONDUCTOR CONFIDENTIAL
18
FSZ[1:0]
Description
00
8-bit
01/10/11
16-bit
[bit9, bit8] FAW[1:0] (FLASH Access Wait) : FLASH access / wait setting
The wait cycle to the FLASH access at CPU mode is set. Because the reading time of the flash memory is
12.5ns, when it accesses the flash memory at 80MHz or more, the access without waiting is impossible.
It is indispensable to insert wait with these bits. Please set it to FAW=1(1wait) when you access it at 80MHz
or more.
Please set these bits before making the clock high-speed when you insert the wait cycle by FAW. Moreover,
please set these bits after setting the clock low-speed when you delete the wait cycle.
FAW[1:0]
Description
00
0 cycle (Initial value)
01
1cycle
10/11
Setting is prohibited
Note:
When 1 wait cycle is set by these bits, the wild register function cannot be used. Please make the core
operation speed to 80MHz or less, and set value of the FAW bits to 2'b00(0cycle) when you use the wild
register function.
[bit7] FDSBL (Flash DiSaBLe) : Flash Disable directive
This bit configures the Flash access disabled state (both reads and writes).
FDSBL
Description
0
Flash access Enable (Initial value)
1
Flash access Disable
[bit6, bit5] Reserved
Reserved bits. The read value is undefined. When writing, always write "0" to these bits.
[bit4] RDYF (ReaDY Flag) : RDY negating instruction when branch is accessed
The wait cycle insertion when the branch is access is directed. When the branch is accessed, the wait cycle
is inserted when this bit is set to "1". The purpose of this is to match the processing cycle when branching.
When the branch access is generated, the control at the wait cycle is made by an internal state of FLASH I/F
when this bit is "0". If the cycle time is not necessary to be secured when the branch access is accepted, the
wait cycle is not inserted. When it is necessary to secure the cycle time, the wait cycle is inserted.
RDYF
Description
0
It depends on the state of FLASH I/F
(Initial value)
1
Wait cycle insert
[bit3 to bit0] Reserved
These bits are reserved. The read value is undefined. When writing, always write "0" to these bits.
MB91520 Series
MN705-00010-1v0-E
1939