
CHAPTER 5 INITIALIZATION INTERFACE
User’s Manual U14272EJ3V0UM
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5.4 Notes on Initialization
This section explains the case in which manipulation by software is necessary after the V
R
4181 has been reset.
When a Cold Reset sequence is executed, the reset exception vector is accessed. Perform manipulation
described here by using the software (handler) for reset exceptions located at the reset exception vector.
5.4.1 CPU core
(1) Coprocessor 0
Be sure to initialize at least the following internal registers of the coprocessor 0 (CP0) after the RTC reset,
RSTSW reset, or Deadman’s Switch reset has been cleared, or the V
R
4181 has returned from the Hibernate
mode.
Config register
Status register
WatchLo register
(2) Cache tag
The contents of the tag RAM of the cache are undefined immediately after a voltage has been applied to the 2.5
V power supply when the RTC reset or Deadman’s Switch reset has been cleared, or when the V
R
4181 has
returned from the Hibernate mode. Before accessing an address at which the cache can be used, therefore, be
sure to initialize the contents of the tag RAM of both the instruction cache and data cache. Use the TagLo
register in CP0 to initialize the tags.
5.4.2 Internal peripheral units
(1) HALTimer
Set the HALTIMERRST bit of the PMUCNTREG register in the PMU to 1 within 4 seconds after clearing the RTC
reset or RSTSW reset. This resets the HALTimer.
(2) Memory controller
Before accessing the DRAM space, be sure to initialize the registers in the memory controller. Especially when
SDRAM is used, initialize SDRAM by executing the procedure described in
6.5.2 MEMCFG_REG (0x0A00
0304)
. A function to operate SDCLK only when SDRAM is accessed, for example, is not valid unless a mode
setting command is issued to SDRAM by using the MEMCFG_REG register.
(3) Clock supply to peripheral units
The clock is not supplied in the default status to the peripheral units such as CSI, AIU, PIU, SIU1, and SIU2, and
the A/D and D/A converters. To start using these units and converters, supply the necessary clock to them by
setting the CMUCLKMSK register in the MBA Host Bridge. If these units are not used or they have finished
being used, mask the clock supply by setting the CMUCLKMSK register.
(4) Alternate-function pins
The function of an alternate-function pin and the I/O direction of the GPIO pins are selected by the registers in
the GIU. Be sure to set these registers in accordance with the unit or the function of the pin to be used. Exercise
care in setting the registers so that signals do not conflict on the board or that a signal whose level is required
does not go into a high-impedance state.