HD6417021 Hitachi Semiconductor, HD6417021 Datasheet - Page 343

• Manufacturer Part Number: HD6417021
• Description: SuperH RISC engine
• Manufacturer: Hitachi Semiconductor

Table 12.1 Pin Configuration
Pin
Watchdog timer overflow
12.1.4
Table 12.2 summarizes the three WDT registers. They are used to select the clock, switch the
WDT mode, and control the reset signal.
Table 12.2
Name
Timer
control/status
register
Timer counter
Reset
control/status
register
Notes: 1. Write by word transfer. It cannot be written in byte or long word.
12.2
12.2.1
The TCNT is an eight-bit readable and writable upcounter. The TCNT differs from other registers
in that it is more difficult to write. See section 12.2.4, Register Access, for details. When the timer
enable bit (TME) in the timer control/status register (TCSR) is set to 1, the timer counter starts
counting pulses of an internal clock source selected by clock select bits 2–0 (CKS2–CKS0) in the
TCSR. When the value of the TCNT overflows (changes from H'FF–H'00), a watchdog timer
overflow signal (WDTOVF) or interval timer interrupt (ITI) is generated, depending on the mode
selected in the WT/IT bit of the TCSR. The TCNT is initialized to H'00 by a reset and when the
TME bit is cleared to 0. It is not initialized in the standby mode.
2. Read by byte transfer. It cannot be read in word or long word.
3. Only 0 can be written in bit 7 to clear the flag.
Register Configuration
Register Descriptions
Timer Counter (TCNT)
WDT Registers
Abbreviation
TCSR
TCNT
RSTCSR
Abbreviation
WDTOVF
R/W
R/(W)*
R/W
R/(W)*
I/O
O
3
3
Initial Value
H'18
H'00
H'3F
Function
Outputs the counter overflow signal in
the watchdog mode
Write*
H'5FFFFB8
H'5FFFFBA
1
Address
Read*
H'5FFFFB8
H'5FFFFB9
H'5FFFFBB
HITACHI 329
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