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
42
Section 4: System Control and Debug Unit
Document
1250_1125-UM100CB-R
The uniprocessor bits and soft-reset bit may be used on the BCM1250 to disable one of the processors. The
clock to the disabled processor will be stopped following reset and it will enter a low power state (lower power
than being left in reset). The processor will be enabled on the next full reset (RESET_L pin asserted,
system_reset bit written with a one or a watchdog double timeout). Following a full reset only CPU0 will be
running and CPU1 will be held in reset. If a uniprocessor system is desired, the CPU0 reset sequence should
check for a multiprocessor environment by reading the multiprocessor bit in the
PrId
(CPU CP0 Processor Id
register) or the uniprocessor bits in the
system_cfg
register. If the system is running as a multiprocessor the
unicpu0 bit should be set in the
system_cfg
register, and the sb_softres bit written with a one to cause the
system to reboot as a uniprocessor.
The
system_scratch
register is a read/write register that is not used by the hardware. It is free for software
use. For example it may be used by firmware to store a pointer to bootstrap information for use by the operating
system, or it may be used to pass (small) messages between the processors before memory is configured.
The value of the register is UNPREDICTABLE following cold reset, the value is preserved over other resets.
The sw_flag bit in the
system_cfg
register may be used to indicate the validity of the scratch value, since the
flag is cleared on a cold reset and preserved over other resets. The sw_flag may also be used by the system
to distinguish between cold resets and others. Software can check the bit after reset: if the bit is zero then the
reset was a cold reset and the bit should be set, if the bit is already set then the reset was some other type
(also see
Table 12: System Identification and Revision Register
system_revision -
00_1002_0000
READ ONLY
Bits
Name
Default
Description
7:0
reserved
8'hff
Reserved, reads as 8'hff.
15:8
revision
xx
Revision of the part. See
31:16
Part
xx
Part type.
BCM1250 16'h1250
16'h1150 (configured as uniprocessor)
16'h1125 (configured as uniprocessor, half L2 aka 1125Y)
BCM1125 16'h1123
BCM1125H 16'h1124
Bits 27:24 Indicate the number of processors.
Bits 23:20 Indicate the L2 cache size (1-128KB, 2-256KB, 5-512KB, 0-1024K).
Bits 19:16 Indicate the peripheral set
(0,2,5 - BCM1250 peripherals,
3 - BCM1125 peripherals, 4 - BCM1125H peripherals).
63:32
wid
xx
Wafer ID.
Table 13: Part Revisions
Part
Stepping
Peripherals
Revision
Nickname
Comment
BCM12500
An
PERIPH_REV1
8’h01 or 8’h02
“Pass1”
Prototype only parts, refer to earlier manual.
BCM1250
An
PERIPH_REV2
8’h03 - 8’h0b
“Pass2”
Inital production BCM1250 parts.
BCM1250
Bn
PERIPH_REV2
8’h10 or 8’h11
“Pass2.2”
BCM1250
Cn
PERIPH_REV3
8’h20
“Pass3”
BCM1250 with peripherals upgraded
BCM1125/H
An
PERIPH_REV3
8’h20 or 8’h21
“Pass1”
Initial production BCM1125/H parts
BCM1125/H
Bn
PERIPH_REV3
8’h30
“Pass2”
Содержание BCM1125
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