7–2
Initialization and Configuration
29 September 1997 – Subject To Change
Input Signals sys_reset_l and dc_ok_h and Booting
After power has reached the proper operating point, signal dc_ok_h must be
asserted. Then, signal sys_reset_l must be deasserted. At this point, the 21164PC
recognizes a powered-up state. If signal dc_ok_h is not asserted, signal sys_reset_l
is forced asserted internally. After sys_reset_l is deasserted, the 21164PC begins the
following sequence of operations:
1.
Icache built-in self-test (BiSt)
2.
An optional automatic Icache initialization, using an external serial ROM
(SROM) interface
3.
Dispatch to the reset PALcode trap entry point (physical location 0)
a.
If step 2 initialized the Icache by using the SROM interface, the cache
should contain code that appears to be at location 0, that is, the cache
should be initialized such that it hits on the dispatch. Typically the code
in the Icache should configure the IPRs in the 21164PC as necessary
before causing any offchip read or write commands. This allows the
21164PC to be configured to match the external system implementation.
b.
If step 2 did not initialize the Icache, the Icache has been flushed by
reset. The reset PALcode trap dispatch misses in the Icache and pro-
duces an offchip read command. The external system implementation
must be compatible with the default configuration of the 21164PC after
reset (refer to Section 7.8). The code that is executed at this point should
complete the 21164PC configuration as necessary.
4.
After configuring the 21164PC, control can be transferred to code anywhere in
memory, including the noncacheable regions. If the SROM interface was used to
initialize the Icache, the Icache can be flushed by a write operation to
IC_FLUSH_CTL after control is transferred. This transfer of control should be
to addresses not loaded in the Icache by the SROM interface or the Icache may
provide unexpected instructions.
5.
Typically, PALbase and any state required by PALcode are initialized and the
console is started (switching out of PALmode and into native mode). The con-
sole code initializes and configures the system and boots an operating system
from an I/O device such as a disk or the network.
Signal sys_reset_l forces the CPU into a known state. Signal sys_reset_l must
remain asserted while signal dc_ok_h is deasserted, and for some period of time
after dc_ok_h assertion. It should remain asserted for at least 400 internal CPU
cycles in length. Then, signal sys_reset_l may be deasserted. Signal sys_reset_l
deassertion need not be synchronous with respect to sysclk. Section 7.8 lists the reset
state of each IPR.