
Philips Semiconductors
System Boot
PRODUCT SPECIFICATION
13-3
system Vendor ID Register,” for more information on the
choice of values.
The MM_CONFIG and PLL_RATIOS registers control
the hardware of the MMI and TM1300 on-chip clock cir-
cuits. These registers are described in detail in Section
12.6, “Memory System Programming.” The boot value
should be set to reflect the exact capabilities of the actual
SDRAM in the system.
The ‘enable internal PCI_CLK generator’ bit determines
the PCI_CLK pin operating mode. If this bit is ‘0’,
PCI_CLK acts compatible with TM1000 and normal PCI
operation, i.e. it is an input pin that takes PCI clock from
the external world. If this bit is ‘1’, an on-chip clock divider
in the XIO logic becomes the source of PCI_CLK, and
the PCI_CLK pin is configured as an output. In the latter
case, the PCI_CLK frequency can be programmed to a
divider of the TM1300 highway clock by setting the
XIO_CTL register ‘Clock Frequency’ divider value. Refer
to Chapter 22, “PCI-XIO External I/O Bus.” Note: This bit
must be set if no external PCI clock is supplied.
The ‘SDRAM prefetchable’ bit is copied to the PCI con-
figuration space register DRAM_BASE and only visible
as bit #3 (P bit) of DRAM_BASE in a PCI configuration
read, but not visible by MMIO access. Its purpose is to
tell the PCI host, that SDRAM reads will cause no side
effects. The host may apply optimizations on PCI ac-
cess, if this bit is set.
The ‘a(chǎn)utonomous/host-assisted boot’ bit determines
whether the system boot logic will continue reading more
information from the EEPROM or halt its operation so the
host can complete system initialization. After the infor-
mation listed in Table 13-2 has been loaded into TM1300
registers, an external PCI host processor can finish the
initialization of TM1300. If no external PCI host proces-
sor is present, the autonomous/host-assisted boot bit
should be set to ‘1’ to allow the system boot logic to load
the information described in the next section.
Table 13-3I2C speed as a function of EEPROM byte 0
BOOT_CLK
bits
EEPROM
speed bit
divider
value
actual I2C
speed
00 (100 MHz)
0 (100 KHz)
1008
99.2 KHz
00
1 (400 KHz)
256
390.6 KHz
01 (75 MHz)
0 (100 KHz)
752
99.7 KHz
01
1 (400 KHz)
192
390.6 KHz
10 (50 MHz)
0 (100 KHz)
512
97.6 KHz
10
1 (400 KHz)
128
390.6 KHz
11 (33 MHz)
0 (100 KHz)
336
98.2 KHz
11
1 (400 KHz)
96
343.8 KHz