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sdc: make some space in memory for buffer CRC

This commit is contained in:
Virgil Dupras 2019-06-18 15:21:58 -04:00
parent 34db493496
commit cac9acca67
1 changed files with 15 additions and 12 deletions
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27
kernel/sdc.asm
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@ -65,12 +65,19 @@
.equ SDC_BUFDIRTY1 SDC_BUFSEC1+2
; The contents of the buffer.
.equ SDC_BUF1 SDC_BUFDIRTY1+1
; CRC bytes for the buffer. They're placed after the contents because that makes
; things easier processing-wise. Because the SD card sends them right after the
; contents, all we need to do is read SDC_BLKSIZE+2.
; IMPORTANT NOTE: This is big endian. The SD card sends the MSB first, so we
; keep it in memory this way.
.equ SDC_CRC1 SDC_BUF1+SDC_BLKSIZE
; second buffer has the same structure as the first.
.equ SDC_BUFSEC2 SDC_BUF1+SDC_BLKSIZE
.equ SDC_BUFSEC2 SDC_CRC1+2
.equ SDC_BUFDIRTY2 SDC_BUFSEC2+2
.equ SDC_BUF2 SDC_BUFDIRTY2+1
.equ SDC_RAMEND SDC_BUF2+SDC_BLKSIZE
.equ SDC_CRC2 SDC_BUF2+SDC_BLKSIZE
.equ SDC_RAMEND SDC_CRC2+2
; *** Code ***
; Wake the SD card up. After power up, a SD card has to receive at least 74
@ -350,8 +357,8 @@ sdcReadBlk:
jr .error ; timeout. error out
.loop1end:
; We received our data token!
; Data packets follow immediately, we have 512 of them to read
ld bc, SDC_BLKSIZE
; Data packets follow immediately, we have 512+CRC of them to read
ld bc, SDC_BLKSIZE+2
ld hl, (SDC_BUFPTR) ; HL --> active buffer's sector
; It sounds a bit wrong to set bufsec and dirty flag before we get our
; actual data, but at this point, we don't have any error conditions
@ -372,9 +379,6 @@ sdcReadBlk:
cpi ; a trick to inc HL and dec BC at the same time.
; P/V indicates whether BC reached 0
jp pe, .loop2 ; BC is not zero, loop
; Read our 2 CRC bytes
call sdcIdle
call sdcIdle
; success! wait until card is ready
call sdcWaitReady
xor a ; success
@ -430,7 +434,10 @@ sdcWriteBlk:
call sdcSendRecv
; Sending our data token!
ld bc, SDC_BLKSIZE
ld bc, SDC_BLKSIZE+2 ; +2 for CRC. (as of now, however, that
; CRC isn't properly updated. Because
; CMD59 isn't enabled, it doesn't
; matter)
ld hl, (SDC_BUFPTR)
inc hl ; sector MSB
inc hl ; dirty flag
@ -442,9 +449,6 @@ sdcWriteBlk:
cpi ; a trick to inc HL and dec BC at the same time.
; P/V indicates whether BC reached 0
jp pe, .loop ; BC is not zero, loop
; Send our 2 CRC bytes. They can be anything
call sdcIdle
call sdcIdle
; Let's see what response we have
call sdcWaitResp
and 0b00011111 ; We ignore the first 3 bits of the response.
@ -464,7 +468,6 @@ sdcWriteBlk:
; Before returning, wait until card is ready
call sdcWaitReady
xor a
; A is already 0
jr .end
.error:
; try to preserve error code