PicoBlaze 8-bit Embedded Microcontroller www.xilinx.com 105
UG129 (v1.1.2) June 24, 2008
RESET Event
RESET Event
The reset event is not an instruction but the response of the PicoBlaze microcontroller
when the RESET input is High. A RESET Event restarts the PicoBlaze microcontroller and
clears various hardware elements, as shown in Table C-3.
A RESET Event is automatically generated immediately following FPGA configuration,
initiated by the FPGA’s internal Global Set/Reset (GSR) signal. After configuration, the
FPGA application generates RESET Event by asserting the RESET input before a rising
CLK clock edge.
The general-purpose registers, the scratchpad RAM, and the program store are not affected
by a RESET Event. The CALL/RETURN stack is a circular buffer, although a RESET Event
essentially resets the CALL/RETURN stack pointer.
Pseudocode
if (RESET input = High) then
; clear Program Counter
PC Å 0
; disable the INTERRUPT input by clearing the INTERRUPT_ENABLE flag
INTERRUPT_INPUT Å 0
; clear the ZERO and CARRY flags
ZERO Å 0
CARRY Å 0
endif
Registers/Flags Altered
Registers: PC, CALL/RETURN stack
Flags: CARRY, ZERO, INTERRUPT_ENABLE
Table C-3: PicoBlaze Reset Values
Resource RESET Event Effect
General-purpose Registers Unaffected.
Program Counter 0
ZERO Flag 0
CARRY Flag 0
INTERRUPT_ENABLE Flag 0
Scratchpad RAM Unaffected.
Program Store Unaffected.
CALL/RETURN Stack Stack Pointer reset.
