
2-36
PowerPC Microprocessor Family: The Bus Interface for 32-Bit Microprocessors
Data retry (DRTRY)
Input/start-up—Used at power-on to select no-DRTRY mode for 603, data
streaming mode for 604, and data streaming mode or no-DRTRY mode for 604e.
For 603 and 604, DRTRY is sampled at the negation of HRESET; if DRTRY is
asserted, no-DRTRY mode is selected (603/604e). If DRTRY is negated at start-
up, DRTRY is enabled. If no-DRTRY or data streaming mode is selected, DRTRY
must be negated during normal operation (
after
HRESET). No-DRTRY mode
provides a one-cycle faster reads; data streaming allows consecutive bursts.
Transfer error acknowledge (TEA) 604—In data streaming mode, the 604 does not recognize TEA the cycle after TA
during a read operation due to the absence of a DRTRY assertion opportunity.
TEA should be asserted for one cycle only.
System Status Signals
Interrupt (INT)
601—INT may be negated after a minimum of three processor clock cycles.
System management interrupt
(SMI)
Supports the system management interrupt not defined by the PowerPC
architecture; not implemented on the 601.
Machine check interrupt (MCP)
This signal is not defined for the 601.
Checkstop input (CKSTP_IN)
Early versions of the 603 identified this signal as CKSTP.
Checkstop output (CKSTP_OUT)
Early versions of the 603 identified this signal as CHECKSTOP.
Hard reset (HRESET)
After assertion, output drivers are released to high impedance within five clocks
(three clocks for the 601) after the assertion of HRESET.
Soft reset (SRESET)
Negation may occur any time after the minimum soft reset pulse width of 2 (10 for
the 601) bus cycles has been met.
Processor State Signals
Reservation (RSRV)
604/604e. RSRV is asserted as late as the fourth cycle after AACK for a read-
atomic operation if the
lwarx
instruction requires a read-atomic operation.
External cache intervention
(L2_INT)
New feature on 604
Time base enable (TBEN)
Time base did not exist on 601.
TLBI synchronization (TLBISYNC) Supports a 603-specific instruction; used at power-on to select 32-bit bus mode
Power Management Signals
Quiescent request
(QUIESC_REQ)
601 only
Quiescent request (QREQ)
603 only. This signal is used at power-on to select a reduced pin mode.
Halted (HALTED)
Power management for the 604
System quiesced (SYS_QUIESC) 601 only
Resume (RESUME)
604 only
Quiescent acknowledge (QACK)
603 only
Run (RUN)
604 only
Table 2-8. Processor Bus Signal Differences (Continued)
Signal(s)
Difference