User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 15: JTAG and Debug Page
427
Table 302: System Control Scan Chain
system_cfg -
00_1002_0008
Bits
Name
Default
Description
0
reserved
ext
Configuration bit for IO_AD[0].
1
reserved
ext
Configuration bit for IO_AD[1]. Indicates source for IO_CLK100. This must not be
changed while the BCM1250 is operating.
2
ldt_minrstcnt
ext
Configuration bit for IO_AD[2]. Broadcom Use Only. This must be zero for normal
operation.
3
ldt_bypass_pll
ext
Configuration bit for IO_AD[3]. Broadcom Use Only. This must be zero for normal
operation.
4
pci_test
ext
Configuration bit for IO_AD[4]. Broadcom Use Only. This must be zero for normal
operation.
5
iob0_div
ext
Configuration bit for IO_AD[5] that controls the clock divider for I/O Bridge 0.
0: IOB0 runs at CPU clock/4, for use with fast CPU clocks.
1: IOB0 runs at CPU clock/3, for use with slow CPU clocks.
6
iob1_div
ext
Configuration bit for IO_AD[6] that controls the clock divider for I/O Bridge 1.
0: IOB1 runs at CPU clock/3, for use with fast CPU clocks.
1: IOB1 runs at CPU clock/2, for use with slow CPU clocks.
11:7
pll_div
ext
Configuration bits for IO_AD[11:7] that select the PLL Divide ratio.
These bits must not be changed while the BCM1250 is operating.
12
ser0_enable
ext
Configuration bit for IO_AD[12].
0: Serial interface 0 is in asynchronous (uart) mode.
1: Serial interface 0 is in synchronous mode.
13
ser0_rstb_en
ext
Configuration bit for IO_AD[13] that allocates GPIO[0] pin to the synchronous serial
interface.
14
ser1_enable
ext
Configuration bit for IO_AD[14].
0: Serial interface 1 is in asynchronous (uart) mode.
1: Serial interface 1 is in synchronous mode.
15
ser1_rstb_en
ext
Configuration bit for IO_AD[15] that allocates GPIO[1] pin to the synchronous serial
interface.
16
pcmcia_enable
ext
Configuration bit for IO_AD[16] that configures the PCMCIA mode.
18:17
boot_mode
ext
Configuration bit for IO_AD[18:17] that configures the boot mode.
00: 32 bit generic bus ROM (multiplexed).
01: 8 bit generic bus ROM (non-multiplexed).
10: SMBus EEPROM <= 16 kbit (read word protocol).
11: SMBus EEPROM > 16kbit (eeprom read word protocol).
19
pci_host
ext
Configuration bit for IO_AD[19], that configures the PCI interface to be host or
device mode.
20
pci_arbiter
ext
Configuration bit for IO_AD[20], that configures the PCI interface to use an internal
or external arbiter. (If the PCI is set in device mode the resistor must be set for an
external arbiter)
21
southOnLDT
ext
Configuration bit for IO_AD[21], that configures the southbridge to be on the
HyperTransport fabric or PCI bus.
22
big_endian
ext
Configuration bit for IO_AD[22], that configures the system to be big or little endian.
23
genclk_en
ext
Configuration bit for IO_AD[23], that enables output of the generic bus clock on
IO_CLK100. If this bit is zero then the IO_CLK100 will be held in a high impedance
state.
24
ldt_test_en
ext
Configuration bit for IO_AD[24]. Broadcom Use Only. This must be zero for normal
operation.