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196 www.xilinx.com PowerPC™ 405 Processor Block Reference Guide
1-800-255-7778 UG018 (v2.0) August 20, 2004
Chapter 4: PowerPC 405 APU Controller
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APU Controller Output Signals
All APU Controller output signals are synchronous with the FCM clock (CPMFCMCLK).
Table 4-7: FCM Interface Output Signals
Signal Function
APUFCMINSTRUCTION[0:31] Instruction being presented to the FCM. Is valid as long as
APUFCMINSTRVALID is high.
APUFCMINSTRVALID This signal is asserted on two conditions:
x A valid APU instruction was decoded by the APU Controller
x An undecoded instruction passed to FCM for decoding
The signal will remain high for one FCM clock cycle, unless
FCMAPUDECODEBUSY is high when it asserts. In that case it stays
high until FCMAPUDECODEBUSY goes low.
APUFCMRADATA[0:31] Instruction operand from GPR(RA).
APUFCMRBDATA[0:31] Instruction operand from GPR(RB).
APUFCMOPERANDVALID Instruction operand valid.
APUFCMFLUSH Flush APU instruction in the FCM. If asserted no
APUFCMWRITEBACKOK signal will be generated
APUFCMWRITEBACKOK Safe for FCM to commit internal state change; the APU Controller can
no longer flush the instruction.
In normal cases, this signal is asserted for one FCM clock cycle. In some
cases when a non-blocking multi-cycle operation is followed by an
autonomous or blocking multi-cycle operation while using a large clock
ratio, the signal may be asserted for two back-to-back FCM clock cycles.
APUFCMLOADDATA[0:31] Data word loaded from storage to the APU register file.
APUFCMLOADDVALID When asserted the data word on the APUFCMLOADDATA[0:31] data
bus is valid.
APUFCMLOADBYTEEN[0:3] Specifies the valid bytes for the word on the load data bus
APUFCMLOADDATA[0:31].
APUFCMENDIAN When asserted, the load/store instruction being presented to the FCM
has true little-endian storage attribute.
APUFCMXERCA Reflects the XerCA bit used for extended arithmetic.
APUFCMDECODED Asserted when the APU Controller decoded the instruction being sent
to the FCM.
APUFCMDECUDI[0:2] Specifies which UDI the APU Controller decoded (binary encoded).
APUFCMDECUDIVALID Valid signals for APUFCMDECUDI.