Information processing unit selecting one of reset vector addresses
View Patent ↗An information processing unit selects one of a plurality of reset vector addresses, and executes an instruction in accordance with the reset vector address selected. A reset memory circuit latches after switch-on a predetermined value as a latch value regardless of a reset signal supplied via a reset terminal. When the reset memory circuit has latched the latch value, an address selection circuit selects one of the reset vector addresses in response to a logical AND of the latch value and a selection signal supplied via a selection terminal. The information processing unit can prevent changes in the reset vector address even though the potential at the reset terminal fluctuates slightly after the switch-on.
1. An information processing unit that executes an instruction specified by one of reset vector addresses at turn-on or at reset by a reset signal, the information processing unit comprising:
storing means for storing reset associated information after turn-on and for outputting the reset associated information in response to the reset signal; and
selecting means for selecting one of the reset vector addresses in accordance with the reset associated information output by the storing means.
2. The information processing unit according to claim 1 , further comprising a reset selection terminal to which a selection signal for specifying one of the reset vector addresses is supplied, wherein
the storing means comprises a latch circuit for latching a predetermined value as a latch value at turn-on; and
the selecting means selects one of the reset vector addresses in response to the latch value held by the latch circuit and to the selection signal supplied via the reset selection terminal.
3. The information processing unit according to claim 2 , wherein the latch value is a power supply voltage, and wherein the selecting means comprises a first AND circuit for selecting a first reset vector address in response to a logical AND of the latch value and the selection signal, and a second AND circuit for selecting a second reset vector address in response to a logical AND of the latch value and an inverted signal of the selection signal.
4. An information processing unit that executes an instruction specified by one of reset vector addresses at turn-on or at reset by a reset signal, the information processing unit comprising:
storing means for storing reset associated information and for outputting the reset associated information in response to the reset signal; and
selecting means for selecting one of the reset vector addresses in accordance with the reset associated information output by the storing means, wherein
the storing means comprises a processor mode register for storing a software reset bit, and wherein
the selecting means selects a first reset vector address when a reset processing is carried out by the reset signal, and selects a second reset vector address different from the first reset vector address when a reset processing is carried out by setting the software reset bit into the processor mode register.
5. An information processing unit that executes an instruction specified by one of reset vector addresses at turn-on or at reset by a reset signal, the information processing unit comprising:
storing means for storing reset associated information and for outputting the reset associated information in response to the reset signal; and
selecting means for selecting one of the reset vector addresses in accordance with the reset associated information output by the storing means, wherein the storing means comprises a register in the information processing unit for storing a cold start/warm start decision flag for making a decision as to whether to execute a cold start involving a reset processing at turn-on, or a warm start involving a reset processing by a reset signal during operation, wherein
the information processing unit further comprises a cold/warm decision circuit for making a decision by the cold start/warm start decision flag as to whether the cold start or warm start is to be executed, and for outputting a cold/warm decision signal, and wherein
the selecting means selects one of the reset vector addresses in response to the cold/warm decision signal when the reset signal is supplied.
6. The information processing unit according to claim 5 , wherein the selecting means comprises a first AND circuit for selecting a first reset vector address in response to a logical AND of the reset signal and the cold/warm decision signal, and a second AND circuit for selecting a second reset vector address in response to a logical AND of the reset signal and an inverted signal of the cold/warm decision signal.
7. The information processing unit according to claim 5 , wherein the selecting means comprises a register with at least one bit for holding the cold/warm decision signal, and selects the reset vector address in response to a value in the register when the reset signal is supplied.