
5-2
PowerPC Microprocessor Family: The Bus Interface for 32-Bit Microprocessors
Table 5-2 describes general differences in how the 601, 603, and 604 implement the system
status signals.
5.2 Resets
There are two types of resets:
Hard resets—These occur with the proper assertion of the HRESET signal, as part
of a system’s power-on reset, or due to other system-dependent occurrences. After a
hard reset occurs, registers and other resources are initialized and instruction
fetching begins at the system reset exception vector at 0xFFF00100.
Soft resets—These occur with the proper assertion of the SRESET signal. When the
SRESET is detected, the machine state is saved in the SRR0 and SRR1 registers, the
MSR is reset, and exception processing continues from the system reset exception
handler which resides at vector offset 0x00100.
Table 5-2. Processor Bus Signal Differences
Signal(s)
Related Exception
Difference
Interrupt (INT)
External interrupt
(0x00500)
For the 601, this signal may be negated after the minimum pulse
width of three processor clock cycles.
System
management
interrupt (SMI)
System management
interrupt
(0x01400)
The system management interrupt exception is not defined by the
PowerPC architecture and not implemented on the 601.
Machine check
(MCP)
Machine check
(0x00200)
This signal is not defined for the 601.
Checkstop input
(CKSTP_IN)
Machine check
(0x00200)
Early versions of the 603 identified this signal as CKSTP.
Checkstop output
(CKSTP_OUT)
Machine check
(0x00200)
Early versions of the 603 identified this signal as CHECKSTOP.
Hard reset
(HRESET)
System reset
(0x00100)
After assertion, output drivers are released to high impedance within
five SYSCLK pulses (three for the 601) after the assertion of
HRESET.
Soft reset
(SRESET)
System reset
(0x00100)
Negation may occur any time after the minimum soft reset pulse
width of 2 (10 for the 601) bus cycles has been met.