BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
26
Section 3: System Overview
Document
1250_1125-UM100CB-R
Figure 7: Decision Tree for Memory Space Address Accesses
R
ESET
The COLDRES_L input is used for power-on reset of the device. It must be held low until the power supplies
are within the operating range and the reference clock is stable. The cold reset will read the PLL multiplier bits
and start the PLL, an internally generated delay allows the PLL to lock before the system is started. At the end
of the cold reset delay reset time configuration information is read from the generic bus IO_AD lines (see
below). The RESET_L input is used to cause a warm reset of the device, this resets all the internal logic but
does not restart the PLL, read the configuration information or wait the cold reset delay (RESET_L need not
be asserted at power-on since the cold reset delay has higher precedence). The end of the cold reset
sequence or the deassertion of RESET_L signal starts the internal reset sequence to establish the internal
state, the SCD will then release the system and CPU0. The device will source the reset signal for the board
(RESETOUT_L), the PCI bus (P_RST_L) and the HyperTransport fabric (LDT_RESET_L and LDT_PWROK
if the link needs a cold reset). These are all driven during the internal reset period and other than P_RST_L
can be asserted separately under software control.
Reset can also be initiated by software or time-out of the watchdog timers. These can be a soft reset which
restarts the part but is not signalled externally or a system reset which will assert RESETOUT_L. The software
initiated system reset will re-sample the configuration information (except for the PLL ratio), the watchdog
system reset will not.
Memory
Read
Error condition
-Some Agent is unable
to determine ownership
Memory Controller
returns Fatal Error
L2 Cache
Read
Memory
Read
Read Shared or Exclusive
(Memory Space Address)
Exclusive
Owner Supplies
Data
Write or Write & Invalidate
(Memory Space Address)
L2 Cache
Write
Memory
Write
SH
D &
EX
C
L2
H
it
L2
M
iss
E
X
C
EXC
& S
HD
Memory Write
L2 Write if Hit
Un
cac
he
ab
le
L1
Cac
heab
le
L2C
A
U
nc
ac
he
ab
le
or
L2
M
as
ter
Ca
ch
eab
le
(in
cl
u
d
es
n
o
n
-c
o
h
er
en
t)
N
ot L
2C
A
L2 Cache
Write
Memory Write
L2 Write if Hit
L2C
A
N
ot L
2C
A
Data Modified
Содержание BCM1125
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