6. Arbitration
144
PowerSpan II User Manual
80A1010_MA001_09
Integrated Device Technology
www.idt.com
The default value of these Mx_EN bits in the PB_ARB_CTRL register are set using the
PWRUP_BOOT option shown in
. When PWRUP_BOOT is selected to boot from PCI, both
Px_LOCKOUT bits in the MISC_CSR register are cleared automatically, even if an EEPROM is not
present.
The processor bus arbiter does not have to be enabled to select either PCI or processor bus boot. The
PWRUP_BOOT option sets the M1_EN bit in the PB_ARB_CTL register and the P1_LOCKOUT and
P2_LOCKOUT bits in the MISC_CSR register. Setting the Px_LOCKOUT bits means any
configuration cycles for PowerSpan II on the PCI bus are retried until the Px_LOCKOUT bits are
cleared from the processor bus or the EEPROM. When PCI_BOOT is set to 1 (boot is from PCI) the
Px_LOCKOUT bits are not set
For more information on power-up options and boot selection, refer to
Table 32: Mx_EN Default State
PWRUP_BOOT
Selection
RST_CSR Register
M1_EN
M2_EN
M3_EN
Boot PCI
PCI_BOOT=1
0
0
0
Boot PB
PCI_BOOT=0
1
0
0