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Sable CPU Module Specification

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Copyright © 1993 Digital Equipment Corporation.<br />

4. The first cycle (the first one or two instructions) at all PALcode entry points may<br />

not execute a conditional branch or any other instruction that uses the jsr stack<br />

hardware. This includes instructions JSR, JMP, RET, COROUTINE,BSR,HW_<br />

REI and all Bxx opcodes except BR, which is allowed.<br />

5. The following table indicates the number of cycles required after a HW_MTPR instruction<br />

before a subsequent HW_REI instruction for the specified IPRs. These<br />

cycles can be insured by inserting one HW_MFPR R31,0 instruction or other<br />

appropriate instruction(s) for each cycle of delay required after the HW_MTPR.<br />

IPR Cycles between HW_MTPR and HW_REI<br />

xTBIS,ASM,ZAP 0<br />

xIER 2<br />

xIRR 2<br />

ICCSR[FPE] 3<br />

ICCSR[ASN] 5<br />

FLUSH_IC[ASM] 6<br />

C.6 Powerup<br />

The table below lists the state of all the IPRs immediately following reset. The table<br />

also specifies which IPRs need to be initialized by power-up PALcode.<br />

Table 92: IPR Reset State<br />

IPR Reset State Comments<br />

ITB_TAG undefined<br />

ITB_PTE undefined<br />

ICCSR cleared except Floating point disabled, single issue mode, VAX mode<br />

ASN, PC0, PC1 enabled, ASN = 0, jsr predictions disabled, branch predictions<br />

disabled, branch history table disabled, performance<br />

counters reset to zero, Perf Cnt0(16b) : Total<br />

Issues/2, Perf Cnt1(12b) : Dcache Misses<br />

ITB_PTE_TEMP undefined<br />

EXC_ADDR undefined<br />

SL_RCV undefined<br />

ITBZAP n/a PALcode must do a itbzap on reset.<br />

ITBASM n/a<br />

ITBIS n/a<br />

PS undefined PALcode must set processor status.<br />

EXC_SUM undefined PALcode must clear exception summary and exception<br />

register write mask by doing 64 reads.<br />

PAL_BASE cleared Cleared on reset.<br />

Cobra Specific ( Privileged Architecture Library Code ) PALcode 235

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