105 lines
1.9 KiB
ArmAsm
105 lines
1.9 KiB
ArmAsm
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//
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// Official Kernal routine, described in:
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//
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// - [RG64] C64 Programmer's Reference Guide - page 295
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// - [CM64] Compute's Mapping the Commodore 64 - page 220
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//
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// CPU registers that has to be preserved (see [RG64]): none
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//
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// Variables used:
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// - KEYTAB - keyboard matrix pointer
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// - DELAY - counter for first delay between key repeats
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// - KOUNT - counter for next delays between key repeats
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// - SHFLAG - SHIFT / CTRL / VENDOR keypress status
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// - NDX - number of characters in keyboard buffer
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// - XMAX - maximum size of keyboard buffer
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// - LSTX - matrix coordinate of last pressed key
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// - LSTSHF - previous status of SHFLAG
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// - MODE - flag, whether charset toggle (SHIFT+VENDOR) is allowed
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#if !CONFIG_SCNKEY_TWW_CTR
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// Routine is heavily inspired by TWW/CTR proposal, see here:
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// - http://codebase64.org/doku.php?id=base:scanning_the_keyboard_the_correct_and_non_kernal_way
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SCNKEY:
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// Handle repeat timer
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lda KOUNT
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beq !+
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dec KOUNT
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!:
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// Prepare for SHFLAG update
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lda SHFLAG
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sta LSTSHF
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lda #$00
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sta SHFLAG
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// XXX retrieve ALT and NO_SCRL status for C128/C65 keyboards
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// Check for any activity
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lda #$00
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sta CIA1_PRA // connect all the rows
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lda #$FF
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cmp CIA1_PRB
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beq scnkey_no_keys
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// Retrieve SHIFT / VENDOR / CTRL status
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ldy #$03
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scnkey_bucky_loop:
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lda kb_matrix_bucky_confmask, y
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sta CIA1_PRA
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lda kb_matrix_bucky_testmask, y
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and CIA1_PRB
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bne !+ // not pressed
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lda SHFLAG
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ora kb_matrix_bucky_shflag, y
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sta SHFLAG
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!:
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dey
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bpl scnkey_bucky_loop
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// Set KEYTAB vector
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jsr scnkey_via_keylog // XXX for some CPUs we have indirect jsr
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// XXX check for joystick activity
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// Scan the keyboard matrix
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ldy #$07
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scnkey_matrix_loop:
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lda kb_matrix_row_keys, y
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sta CIA1_PRA
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lda kb_matrix_bucky_filter, y
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ora CIA1_PRB
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// XXX
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dey
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bpl scnkey_matrix_loop
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// XXX
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scnkey_no_keys:
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lda #$FF
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sta LSTX
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rts
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scnkey_via_keylog:
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jmp (KEYLOG)
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#endif // no CONFIG_SCNKEY_TWW_CTR
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