CHAPTER 32 CAUTIONS FOR WAIT
User’s Manual U16899EJ2V0UD
496
32.2 Peripheral Hardware That Generates Wait
Table 32-1 lists the registers that issue a wait request when accessed by the CPU, and the number of CPU wait
clocks.
Table 32-1. Registers That Generate Wait and Number of CPU Wait Clocks
Peripheral Hardware
Register
Access
Number of Wait Clocks
Watchdog timer
WDTM
Write
3 clocks (fixed)
Serial interface UART0
ASIS0
Read
1 clock (fixed)
Serial interface UART6
ASIS6
Read
1 clock (fixed)
ADM Write
ADS Write
PFM Write
PFT Write
2 to 5 clocks
Note
(when ADM.5 flag = “1”)
2 to 9 clocks
Note
(when ADM.5 flag = “0”)
ADCR Read 1 to 5 clocks
(when ADM.5 flag = “1”)
1 to 9 clocks
(when ADM.5 flag = “0”)
A/D converter
<Calculating maximum number of wait clocks>
{(1/f
MACRO
)
×
2/(1/f
CPU
)} + 1
*The result after the decimal point is truncated if it is less than t
CPUL
after it has been multiplied by
(1/f
CPU
), and is rounded up if it exceeds t
CPUL
.
f
MACRO
:
Macro operating frequency
(When bit 5 (FR2) of ADM = “1”: f
X
/2, when bit 5 (FR2) of ADM = “0”: f
X
/2
2
)
f
CPU
:
CPU clock frequency
t
CPUL
:
Low-level width of CPU clock
Note No wait cycle is generated for the CPU if the number of wait clocks calculated by the above expression is 1.
Caution When the CPU is operating on the subsystem clock and the high-speed system clock is stopped
(MCC = 1), do not access the registers listed above using an access method in which a wait request
is issued.
Remark The clock is the CPU clock (f
CPU
).
Содержание MuPD78F0132H
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