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R01UH0336EJ0102 Rev.1.02
Page 126 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 3 CPU System Function
3.2.3
HALT Mode
(1)
Setting and Operation of HALT Mode
In normal operation mode, HALT mode is selected by executing a dedicated
instruction (the HALT instruction). In HALT mode, pipeline operation of the
CPU is stopped but clock signals continue to be supplied to the clock
oscillation circuit and other on-chip peripheral modules.
This allows the stopping of program execution while retaining the on-chip RAM
in the same condition as before the HALT mode setting. Furthermore, on-chip
peripheral modules that are independent of instruction processing by the CPU
continue to operate. The average current drawn by the overall system can be
reduced by alternation between the HALT and normal operating modes.
(2)
Cancelling HALT Mode
The transition from HALT mode to normal operating mode is in response to the
input of a reset, or to the generation of an interrupt or other exception.
Following the acceptance of any interrupt or exception, program counting by
the program counter resumes from the address of the instruction after the
HALT instruction.
Input of any of the following resets or the generation of any of the following
interrupts or exceptions constitutes a request for release from HALT mode.
• Reset input (RESET, WDTA0RES, CLMA0RES to CLMA2RES, LVIRES,
SGARES, DBRES)
• EI level maskable interrupt (EIINT)
• FE level maskable interrupt (FEINT)
• FE level non-maskable interrupt (FENMI)
• Peripheral device protection exception (PPI)
• Timing supervision exception (TSI)
• System error exception (SYSERR)
Table 3-4
State of Operations in HALT Mode
Function
State of Operations
Clock generator
Operating
CPU system clock
Operating
Peripheral clock (PCLK)
Operating
CPU
Stopped
Peripheral I/O
Operating
Internal data
The states of internal data for which reprogramming is not possible
while the CPU is stopped, such as the values of registers, status bits,
and other data in the CPU and on-chip RAM, are retained from before
the setting of HALT mode.