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sdc: support 24-bit addressing
Needed if we want to compile the kernel and zasm from within a SD card. I didn't go straight for 32-bit because it was significantly more complex and 24-bit give us 16M. Enough to go on for a while...
This commit is contained in:
Virgil Dupras
parent
605c631dc0
commit
92a04f4627
@ -5,7 +5,12 @@ sdctMain:
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ld de, SDCT_RAMSTART
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.wLoop:
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ld a, (de)
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call sdcPutC
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; To avoid overwriting important data and to test the 24-bit addressing,
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; we set DE to 12 instead of zero
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push de ; <|
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ld de, 12 ; |
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call sdcPutC ; |
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pop de ; <|
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jr nz, .error
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inc hl
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inc de
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@ -23,7 +28,10 @@ sdctMain:
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ld hl, 0
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ld de, SDCT_RAMSTART
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.rLoop:
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call sdcGetC
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push de ; <|
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ld de, 12 ; |
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call sdcGetC ; |
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pop de ; <|
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jr nz, .error
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ex de, hl
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cp (hl)
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137
kernel/sdc.asm
137
kernel/sdc.asm
@ -59,16 +59,16 @@
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; This is a pointer to the currently selected buffer. This points to the BUFSEC
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; part, that is, two bytes before actual content begins.
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.equ SDC_BUFPTR SDC_RAMSTART
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; Sector number currently in SDC_BUF1.
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; Sector number currently in SDC_BUF1. Little endian like any other z80 word.
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.equ SDC_BUFSEC1 SDC_BUFPTR+2
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; Whether the buffer has been written to. 0 means clean. 1 means dirty.
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.equ SDC_BUFDIRTY1 SDC_BUFSEC1+1
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.equ SDC_BUFDIRTY1 SDC_BUFSEC1+2
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; The contents of the buffer.
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.equ SDC_BUF1 SDC_BUFDIRTY1+1
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; second buffer has the same structure as the first.
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.equ SDC_BUFSEC2 SDC_BUF1+SDC_BLKSIZE
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.equ SDC_BUFDIRTY2 SDC_BUFSEC2+1
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.equ SDC_BUFDIRTY2 SDC_BUFSEC2+2
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.equ SDC_BUF2 SDC_BUFDIRTY2+1
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.equ SDC_RAMEND SDC_BUF2+SDC_BLKSIZE
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@ -301,21 +301,18 @@ sdcSetBlkSize:
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pop hl
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ret
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; Read block index specified in A and place the contents in buffer pointed to
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; Read block index specified in DE and place the contents in buffer pointed to
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; by (SDC_BUFPTR).
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; Doesn't check CRC. If the operation is a success, updates buffer's sector to
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; the value of A.
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; the value of DE.
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; Returns 0 in A if success, non-zero if error.
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sdcReadBlk:
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push bc
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push de
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push hl
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out (SDC_PORT_CSLOW), a
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ld hl, 0 ; read single block at addr A
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ld d, 0
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ld e, a ; E isn't touched in the rest of the routine
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; and holds onto our original A
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ld hl, 0
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; DE already has the correct value
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ld a, 0b01010001 ; CMD17
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call sdcCmd
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or a ; cp 0
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@ -341,7 +338,10 @@ sdcReadBlk:
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; actual data, but at this point, we don't have any error conditions
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; left, success is guaranteed. To avoid needlesssly INCing hl, let's
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; set sector and dirty along the way
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ld a, e ; sector number
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ld a, e ; sector number LSB
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ld (hl), a
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inc hl ; sector number MSB
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ld a, d
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ld (hl), a
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inc hl ; dirty flag
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xor a ; unset
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@ -368,7 +368,6 @@ sdcReadBlk:
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.end:
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out (SDC_PORT_CSHIGH), a
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pop hl
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pop de
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pop bc
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ret
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@ -377,7 +376,8 @@ sdcReadBlk:
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; A returns 0 in A on success (with Z set), non-zero (with Z unset) on error.
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sdcWriteBlk:
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push hl
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ld hl, (SDC_BUFPTR) ; HL points to sector
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ld hl, (SDC_BUFPTR) ; HL points to sector LSB
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inc hl ; sector MSB
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inc hl ; now to dirty flag
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xor a
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cp (hl)
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@ -389,11 +389,13 @@ sdcWriteBlk:
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push de
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out (SDC_PORT_CSLOW), a
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dec hl ; sector
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dec hl ; sector MSB
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ld a, (hl)
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ld d, a
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dec hl ; sector LSB
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ld a, (hl)
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ld hl, 0 ; write single block at addr A
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ld d, 0
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ld e, a
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ld hl, 0 ; high addr word always zero, DE already set
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ld a, 0b01011000 ; CMD24
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call sdcCmd
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or a ; cp 0
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@ -411,6 +413,7 @@ sdcWriteBlk:
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; Sending our data token!
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ld bc, SDC_BLKSIZE
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ld hl, (SDC_BUFPTR)
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inc hl ; sector MSB
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inc hl ; dirty flag
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inc hl ; beginning of contents
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@ -434,6 +437,7 @@ sdcWriteBlk:
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call sdcWaitResp
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; Success! Now let's unset the dirty flag
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ld hl, (SDC_BUFPTR)
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inc hl ; sector MSB
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inc hl ; dirty flag
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xor a
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ld (hl), a
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@ -456,72 +460,83 @@ sdcWriteBlk:
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pop hl
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ret
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; Considering the first 7 bits of HL, select the most appropriate of our two
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; Considering the first 15 bits of EHL, select the most appropriate of our two
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; buffers and, if necessary, sync that buffer with the SD card. If the selected
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; buffer doesn't have the same sector as what HL asks, load that buffer from
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; buffer doesn't have the same sector as what EHL asks, load that buffer from
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; the SD card.
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; If the dirty flag is set, we write the content of the in-memory buffer to the
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; SD card before we read a new sector.
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; Returns Z on success, not-Z on error (with the error code from either
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; sdcReadBlk or sdcWriteBlk)
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sdcSync:
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; HL points to the character we're supposed to read or right now. Let's
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; extract the wanted sector from this.
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push de
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; Given a 24-bit address in EHL, extracts the 15-bit sector from it and
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; place it in DE.
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; We need to shift both E and H right by one bit
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srl e ; sets Carry
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ld d, e
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ld a, h
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srl a ; A --> the requested sector number
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push hl ; Save the requested addr for later
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ld l, a
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rra ; takes Carry
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ld e, a
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; Let's first see if our first buffer has our sector
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ld a, (SDC_BUFSEC1)
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cp l
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ld a, (SDC_BUFSEC1) ; sector LSB
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cp e
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jr nz, .notBuf1
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ld a, (SDC_BUFSEC1+1) ; sector MSB
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cp d
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jr z, .buf1Ok
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.notBuf1:
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; Ok, let's check for buf2 then
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ld a, (SDC_BUFSEC2)
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cp l
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ld a, (SDC_BUFSEC2) ; sector LSB
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cp e
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jr nz, .notBuf2
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ld a, (SDC_BUFSEC2+1) ; sector MSB
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cp d
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jr z, .buf2Ok
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.notBuf2:
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; None of our two buffers have the sector we need, we'll need to load
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; a new one.
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; We select our buffer depending on which is dirty. If both are on the
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; same status of dirtiness, we pick any (the first in our case). If one
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; of them is dirty, we pick the clean one.
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ld hl, SDC_BUFSEC1
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ld a, (SDC_BUFDIRTY1)
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or a ; is buf1 dirty?
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jr z, .ready ; no? good, that's our buffer
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; yes? then buf2 is our buffer.
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ld hl, SDC_BUFSEC2
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.ready:
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; At this point, HL points to one of our two buffers, the good one.
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; Let's save it to SDC_BUFPTR
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ld (SDC_BUFPTR), hl
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; You remember that HL we saved a long time ago? Now's the time to
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; bring it back.
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pop hl
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push de ; <|
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ld de, SDC_BUFSEC1 ; |
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ld a, (SDC_BUFDIRTY1) ; |
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or a ; | is buf1 dirty?
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jr z, .ready ; | no? good, that's our buffer
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; yes? then buf2 is our buffer. ; |
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ld de, SDC_BUFSEC2 ; |
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; |
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.ready: ; |
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; At this point, DE points to one o|f our two buffers, the good one.
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; Let's save it to SDC_BUFPTR |
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ld (SDC_BUFPTR), de ; |
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; |
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pop de ; <|
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; We have to read a new sector, but first, let's write the current one
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; if needed.
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call sdcWriteBlk
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ret nz ; error
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; Let's read our new sector
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ld a, h
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srl a
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jp sdcReadBlk ; returns
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jr nz, .end ; error
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; Let's read our new sector in DE
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call sdcReadBlk
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jr .end
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.buf1Ok:
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ld hl, SDC_BUFSEC1
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ld (SDC_BUFPTR), hl
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pop hl
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ret
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ld de, SDC_BUFSEC1
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ld (SDC_BUFPTR), de
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jr .end
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.buf2Ok:
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ld hl, SDC_BUFSEC2
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ld (SDC_BUFPTR), hl
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pop hl
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ld de, SDC_BUFSEC2
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ld (SDC_BUFPTR), de
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; to .end
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.end:
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pop de
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ret
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; *** shell cmds ***
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@ -539,12 +554,13 @@ sdcInitializeCmd:
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; way, no need for special conditions.
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; initialize variables
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ld hl, SDC_BUFSEC1
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xor a
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ld (SDC_BUFPTR), hl
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ld de, 0
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call sdcReadBlk ; read sector 0 in buf1
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ret nz
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ld hl, SDC_BUFSEC2
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inc a
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ld (SDC_BUFPTR), hl
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inc de
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jp sdcReadBlk ; read sector 1 in buf2, returns
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; Flush the current SDC buffer if dirty
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@ -561,13 +577,17 @@ sdcFlushCmd:
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; *** blkdev routines ***
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; Make HL point to its proper place in SDC_BUF.
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; HL currently is an offset to read in the SD card. Load the proper sector in
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; memory and make HL point to the correct data in the memory buffer.
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; EHL currently is a 24-bit offset to read in the SD card. E=high byte,
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; HL=low word. Load the proper sector in memory and make HL point to the
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; correct data in the memory buffer.
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_sdcPlaceBuf:
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call sdcSync
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ret nz ; error
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; At this point, we have the proper buffer in place and synced in
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; (SDC_BUFPTR). Only the 9 low bits of HL are important.
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push de
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ld de, (SDC_BUFPTR)
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inc de ; sector LSB
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inc de ; dirty flag
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inc de ; contents
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ld a, h ; high byte
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@ -617,6 +637,7 @@ sdcPutC:
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; Now, let's set the dirty flag
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ld a, 1
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ld hl, (SDC_BUFPTR)
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inc hl ; sector MSB
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inc hl ; point to dirty flag
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ld (hl), a ; set dirty flag
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xor a ; ensure Z
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@ -1,4 +1,9 @@
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CFSTARGETS = cfsin/zasm cfsin/sdct cfsin/user.h
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# source files required to build os.bin. We copy them in cfsin so that we can
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# build the same kernel from within the RC2014.
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KERNEL_SRCS = err.h acia.asm blockdev.asm blockdev_cmds.asm core.asm fs.asm \
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fs_cmds.asm mmap.asm parse.asm pgm.asm sdc.asm shell.asm stdio.asm
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CFSTARGETS = $(addprefix cfsin/, zasm sdct at28w user.h $(KERNEL_SRCS))
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BASE = ../../..
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TOOLS = $(BASE)/tools
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ZASM = $(TOOLS)/zasm.sh
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@ -24,5 +29,16 @@ cfsin/zasm: $(ZASMBIN)
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cfsin/sdct: $(ZASMBIN)
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$(ZASM) $(APPS) user.h < $(APPS)/sdct/glue.asm > $@
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cfsin/at28w: $(ZASMBIN)
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$(ZASM) $(APPS) $(KERNEL) user.h < $(APPS)/at28w/glue.asm > $@
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cfsin/user.h: user.h
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cp $< $@
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cfsin/err.h: $(KERNEL)/err.h
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cp $< $@
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cfsin/%.asm: $(KERNEL)/%.asm
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cp $< $@
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.PHONY: clean
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clean:
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rm -f $(CFSTARGETS) sdcard.cfs os.bin
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@ -1,10 +1,10 @@
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; classic RC2014 setup (8K ROM + 32K RAM) and a stock Serial I/O module
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; The RAM module is selected on A15, so it has the range 0x8000-0xffff
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.equ RAMSTART 0x8000
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; kernel RAM usage, because of SDC, is a bit high and bring us almost to 0x9c00
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; kernel RAM usage, because of SDC, is a bit high and bring us almost to 0x9e00
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; We allocate at least 0x100 bytes for RAM, which is why we have this threshold.
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; for the stack.
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.equ RAMEND 0x9d00
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.equ RAMEND 0xa000
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.equ PGM_CODEADDR RAMEND
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.equ ACIA_CTL 0x80 ; Control and status. RS off.
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.equ ACIA_IO 0x81 ; Transmit. RS on.
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@ -44,11 +44,12 @@ jp aciaInt
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jp printHexPair
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jp sdcGetC
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jp sdcPutC
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jp blkGetC
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#include "err.h"
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#include "core.asm"
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#include "parse.asm"
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.equ ACIA_RAMSTART RAMSTART
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.equ ACIA_RAMSTART RAMSTART
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#include "acia.asm"
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.equ BLOCKDEV_RAMSTART ACIA_RAMEND
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.equ BLOCKDEV_COUNT 4
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@ -1,4 +1,4 @@
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.equ USER_CODE 0x9d00
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.equ USER_CODE 0xa000
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.equ USER_RAMSTART USER_CODE+0x1800
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.equ FS_HANDLE_SIZE 6
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.equ BLOCKDEV_SIZE 8
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@ -31,3 +31,4 @@
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.equ printHexPair 0x4d
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.equ sdcGetC 0x50
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.equ sdcPutC 0x53
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.equ blkGetC 0x56
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