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https://opencores.org/ocsvn/eco32/eco32/trunk
Subversion Repositories eco32
[/] [eco32/] [tags/] [eco32-0.22/] [simtest/] [rom/] [romboot.s] - Rev 168
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; ; romboot.s -- the ROM bootstrap ; .set termbase,0xF0300000 ; terminal base address .set diskbase,0xF0400000 ; disk base address .set diskbuffer,0xF0480000 ; disk buffer address .set virtbase,0xC0000000 ; base of kernel virtual addresses .set virtboot,0xC0000000 ; where to start the bootstrap sector .set stacktop,0xC0100000 ; where the stack is located .set PSW,0 .set TLB_INDEX,1 .set TLB_ENTRY_HI,2 .set TLB_ENTRY_LO,3 .set TLB_ENTRIES,32 .code reset: j start interrupt: j interrupt miss: j miss start: mvts $0,PSW ; disable interrupts and user mode mvts $0,TLB_ENTRY_LO ; invalidate all TLB entries add $8,$0,virtbase ; by impossible virtual page number add $9,$0,$0 add $10,$0,TLB_ENTRIES tlblp: mvts $8,TLB_ENTRY_HI mvts $9,TLB_INDEX tbwi add $8,$8,0x1000 ; all entries must be different add $9,$9,1 bne $9,$10,tlblp add $29,$0,stacktop ; set stack pointer add $4,$0,signon ; show sign-on message jal mout cmdlp: add $4,$0,prompt ; show prompt jal mout jal echo sub $8,$2,0x0D ; '<ret>'? beq $8,$0,rcmdlp sub $8,$2,'b' ; 'b'? beq $8,$0,boot add $4,$0,'?' ; unknown command jal cout rcmdlp: jal crlf j cmdlp boot: jal crlf add $8,$0,diskbase ; check if disk present add $9,$0,1000000 ; retry count boot1: ldw $16,$8,0 ; get status and $10,$16,0x20 ; check if disk ready bne $10,$0,boot2 ; ready - exit loop sub $9,$9,1 bne $9,$0,boot1 ; try again j nodsk ; enough retries - error boot2: ldw $16,$8,12 ; check if capacity greater than 0 beq $16,$0,nodsk ; no - report error add $4,$0,dfmsg ; say that we found a disk jal mout add $4,$16,$0 ; and how many sectors it has jal wout add $4,$0,sctmsg jal mout add $8,$0,diskbase ; try to load the boot sector add $9,$0,1 ; sector count stw $9,$8,4 add $9,$0,0 ; first sector stw $9,$8,8 add $9,$0,1 ; start command stw $9,$8,0 dskwt: ldw $9,$8,0 and $9,$9,0x10 ; done? beq $9,$0,dskwt ldw $9,$8,0 and $9,$9,0x08 ; error? bne $9,$0,dskerr add $8,$0,diskbuffer ; copy sector add $9,$0,virtboot add $10,$0,512 dskcp: ldw $11,$8,0 stw $11,$9,0 add $8,$8,4 add $9,$9,4 sub $10,$10,4 bne $10,$0,dskcp add $8,$0,virtboot ; signature present? ldbu $9,$8,512-2 sub $9,$9,0x55 bne $9,$0,nosig ldbu $9,$8,512-1 sub $9,$9,0xAA bne $9,$0,nosig jalr $8 ; finally... lift off j cmdlp ; in case we ever return to here nodsk: add $4,$0,dnfmsg ; there is no disk jal mout j cmdlp dskerr: add $4,$0,demsg ; disk error jal mout j cmdlp nosig: add $4,$0,nsgmsg ; no signature jal mout j cmdlp crlf: sub $29,$29,4 stw $31,$29,0 add $4,$0,0x0D jal cout add $4,$0,0x0A jal cout ldw $31,$29,0 add $29,$29,4 jr $31 mout: sub $29,$29,8 stw $31,$29,4 stw $16,$29,0 add $16,$4,$0 mout1: ldbu $4,$16,0 beq $4,$0,mout2 jal cout add $16,$16,1 j mout1 mout2: ldw $16,$29,0 ldw $31,$29,4 add $29,$29,8 jr $31 wout: sub $29,$29,8 stw $31,$29,4 stw $16,$29,0 add $16,$4,$0 slr $4,$16,16 jal hout add $4,$16,$0 jal hout ldw $16,$29,0 ldw $31,$29,4 add $29,$29,8 jr $31 hout: sub $29,$29,8 stw $31,$29,4 stw $16,$29,0 add $16,$4,$0 slr $4,$16,8 jal bout add $4,$16,$0 jal bout ldw $16,$29,0 ldw $31,$29,4 add $29,$29,8 jr $31 bout: sub $29,$29,8 stw $31,$29,4 stw $16,$29,0 add $16,$4,$0 slr $4,$16,4 jal nout add $4,$16,$0 jal nout ldw $16,$29,0 ldw $31,$29,4 add $29,$29,8 jr $31 nout: sub $29,$29,4 stw $31,$29,0 and $4,$4,0x0F add $4,$4,0x30 sub $8,$4,0x3A blt $8,$0,nout1 add $4,$4,7 nout1: jal cout ldw $31,$29,0 add $29,$29,4 jr $31 cin: add $8,$0,termbase cin1: ldw $9,$8,0 and $9,$9,1 beq $9,$0,cin1 ldw $2,$8,4 jr $31 cout: add $8,$0,termbase cout1: ldw $9,$8,8 and $9,$9,1 beq $9,$0,cout1 stw $4,$8,12 jr $31 echo: sub $29,$29,4 stw $31,$29,0 jal cin add $4,$0,$2 jal cout ldw $31,$29,0 add $29,$29,4 jr $31 signon: .byte 0x0D, 0x0A .byte "ROM Bootstrap Version 1" .byte 0x0D, 0x0A, 0x0D, 0x0A, 0 prompt: .byte "#" .byte 0 dnfmsg: .byte "Disk not found!" .byte 0x0D, 0x0A, 0 dfmsg: .byte "Disk with 0x" .byte 0 sctmsg: .byte " sectors found, booting..." .byte 0x0D, 0x0A, 0 demsg: .byte "Disk error!" .byte 0x0D, 0x0A, 0 nsgmsg: .byte "MBR signature missing!" .byte 0x0D, 0x0A, 0
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