HD6417615 Hitachi Semiconductor, HD6417615 Datasheet - Page 147

• Manufacturer Part Number: HD6417615
• Description: Hardware Manual
• Manufacturer: Hitachi Semiconductor

4.2
4.2.1
Resets have the highest priority of any exception source. There are two types of resets: manual
resets and power-on resets. As table 4.5 shows, both types of resets initialize the internal status of
the CPU. In power-on resets, all registers of the on-chip peripheral modules are initialized; in
manual resets, registers of all on-chip peripheral modules except the bus state controller (BSC),
user break controller (UBC), pin function controller (PFC), and frequency modification register
(FMR) are initialized. (Use the power-on reset when turning the power on.)
Table 4.5
Type
Power-on reset
Manual reset
4.2.2
When the NMI pin is high and the RES pin is driven low, the device performs a power-on reset.
For a reliable reset, the RES pin should be kept low for at least the duration of the oscillation
settling time (when the PLL circuit is halted) or for 20t
During a power-on reset, the CPU’s internal state and all on-chip peripheral module registers are
initialized. See appendix B, Pin States, for the state of individual pins in the power-on reset state.
In a power-on reset, power-on reset exception handling starts when the NMI pin is kept high and
the RES pin is first driven low for a set period of time and then returned to high. The CPU will
then operate as follows:
1. The initial value (execution start address) of the program counter (PC) is fetched from the
2. The initial value of the stack pointer (SP) is fetched from the exception vector table.
3. The vector base register (VBR) is cleared to H'00000000 and the interrupt mask bits (I3–I0) of
4. The values fetched from the exception vector table are set in the PC and SP, and the program
exception vector table.
the status register (SR) are set to H'F (1111).
begins executing.
Resets
Types of Resets
Power-On Reset
Types of Resets
NMI Pin
High
Low
Transition to Reset Status
Conditions for
RES Pin
Low
Low
CPU
Initialized
Initialized
pcyc
(when the PLL circuit is running).
On-Chip Peripheral Modules
Initialized
Initialized except for BSC, UBC,
PFC, and frequency modification
register (FMR)
Internal Status
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