
File: boot.fm5, modified 7/23/99
PRELIMINARY INFORMATION
12-1
System Boot
Chapter 12
by Gert Slavenburg, Bob Bradfield, and Hani Salloum
12.1
NEW IN TM1100
A new bit in the boot EEPROM allows enabling of an in-
ternal PCI_CLK clock source for low-cost standalone
systems
12.2
TM1100 BOOT SEQUENCE
OVERVIEW
Before a TM1100 system can begin operating, the main-
memory interface registers and on-chip clock ratio regis-
ter must be configured. Since the DSPCPU cannot begin
operating until after these registers and circuits are ini-
tialized, the DSPCPU cannot be relied upon to initialize
these resources. Consequently, TM1100 needs an inde-
pendent bootstrap facility for the low-level initialization.
TM1100 implements low-level system initialization by
combining a small block of on-chip system boot logic with
a single external serial boot EEPROM connected to the
I2C interface are slow but have the advantages of being
space-efficient and inexpensive. The amount of informa-
tion needed for initial system boot is small, so speed is
not a concern.
The TM1100 system boot block performs differently for
each of the two major types of TM1100 system. The
most significant bit of the tenth byte in the external EE-
PROM determines the system boot procedure and must
match the system configuration.
In the first type of system, host-assisted bootstrapping
takes place. In this configuration, a TM1100 device is in-
tegrated into a system where some other processor
serves as the host. For example, a TM1100 chip might
be part of a PCI card in a standard personal computer
(PC). In this case, the TM1100 system boot need only
load enough information from the serial EEPROM to con-
figure the on-chip timing circuits and main-memory inter-
face; the host processor can perform all other TM1100
setup chores.
In the second type of system, autonomous bootstrapping
takes place. In this configuration, a TM1100 device
serves as the host (main) processor; consequently, the
TM1100 system boot must perform more work. In addi-
tion to configuring on-chip timing and the main-memory
interface, the system boot must set the base addresses
of the main-memory and MMIO address apertures and
load into main memory a level 1 bootstrap program for
the DSPCPU.
Only the first ten bytes of the serial EEPROM are needed
when TM1100 is not the host PCI processor; thus, such
systems can use a very low-cost 128-byte EEPROM de-
vice. When TM1100 serves as the system’s host proces-
sor, the boot logic permits almost 2K bytes of storage for
Figure 12-1. The system boot logic uses the I2C in-
terface to access a serial EEPROM that contains
main-memory and system timing information.
4.7K
TM1100
System Boot
Block
I2C Interface
Serial
EEPROM
SCL
SDA
4.7K
Vdd
Table 12-1. System Boot Features
Characteristic
Comments
Boot Congurations
Supported
Host assisted, e.g., TM1100 is a
PCI slave in a standard PC.
Autonomous, e.g., TM1100 is the
host PCI processor.
ROM Device Types
Supported
Single standard I2C serial
EEPROMs from 128 bytes to 2K
bytes in size.
EEPROMs connect via the
tm1100’s built-in two-wire I2C inter-
face.
The use of EEPROMs with hard-
ware Write Protect (WP) is recom-
mended. A jumper on WP allows
user control over in-system repro-
gramming using the I2C interface.
The EEPROM must respond to I2C
device address 1010.
ROM Device exam-
ples
Atmel 24C01A (128 bytes, WP)
Atmel 24C08 (1Kbytes, WP)
Atmel 24C16 (2Kbytes, WP).
ROM size
From 128 bytes to 2K bytes (one
device) for initial program load.