CHAPTER 3 CPU FUNCTION
94
User’s Manual U14359EJ4V0UM
3.4.9
Specific registers
Specific registers are registers that are protected from being written with illegal data due to erroneous program
execution, etc. The V850E/MA1 has three specific registers, the power-save control register (PSC) (refer to
9.5.2 (3)
Power-save control register (PSC)
), clock control register (CKC) (refer to
9.3.4 Clock control register (CKC)
), and
flash programming mode control register (FLPMC). Disable DMA transfer when writing to a specific register.
There are also two protection registers supporting write operations for specific registers to avoid an unexpected
stoppage of the application system due to erroneous program execution. These two registers are the command
register (PRCMD) and peripheral command register (PHCMD) (refer to
9.5.2 (2) Command register (PRCMD)
and
9.3.3 Peripheral command register (PHCMD)
).
3.4.10 System wait control register (VSWC)
The system wait control register (VSWC) is a register that controls the bus access wait for the on-chip peripheral
I/O registers.
Access to on-chip peripheral I/O registers is made in 3 clocks (without wait), however, in the V850E/MA1 waits may
be required depending on the operation frequency. Set the values described in the table below to the VSWC in
accordance with the operation frequency used.
This register can be read/written in 8-bit units (address: FFFFF06EH, initial value: 77H).
Operation Frequency (f
XX
)
Set Value of VSWC
Number of Waits for On-chip
Peripheral I/O Register Access
4 MHz
≤
f
XX
< 33 MHz
11H
2
33 MHz
≤
f
XX
≤
50 MHz
12H (recommended),
or 13H
When VSWC = 12H: 3 (recommended),
or when VSWC = 13H: 4
Remark
If the timing of changing a count value contend with the timing of accessing a register when accessing
a register having status flags that indicate the status of the internal peripheral functions (such as
ASIFn) or a register that indicates the count value of a timer (such as TMCn), the register access is
retried. As a result, it may take a longer time to access an internal peripheral I/O register.
3.4.11 Cautions
When using the V850E/MA1, the following registers must be set in the beginning.
•
System wait control register (VSWC)
(See
3.4.10 System wait control register (VSWC)
)
•
Clock control register (CKC)
(See
9.3.4 Clock control register (CKC)
)
After setting VSWC and CKC, set other registers if necessary.
To use the external bus, initialize each register in the following sequence after setting the above registers.
<1> Set each pin to the control mode by setting each port-related register.
<2> Select a chip select space by using chip area select control register n (CSCn) (n = 0, 1).
<3> Specify the type of memory of each chip select space by using bus cycle type configuration register n
(BCTn).
Содержание V850E/MA1
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