148 lines
3.8 KiB
ArmAsm
148 lines
3.8 KiB
ArmAsm
//
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// Official Kernal routine, described in:
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//
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// - [RG64] C64 Programmer's Reference Guide - page 286
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// - [CM64] Compute's Mapping the Commodore 64 - page 231
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// - IEC reference at http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
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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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// Expects that SETLFS and SETNAM are called before hand.
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// $YYXX = load address.
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// (ignored if SETLFS channel = 1, i.e., like ,8,1)
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// If A=1 then VERIFY instead of LOAD.
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// On exit, $YYXX is the highest address into which data
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// will have been placed.
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// XXX honor MSGFLG bit 6
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// XXX add VERIFY support
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LOAD:
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// Are we loading or verifying?
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sta VERCKK
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// Store start address of LOAD
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stx STAL+0
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sty STAL+1
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// Reset status
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jsr kernalstatus_reset
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#if CONFIG_MEMORY_MODEL_60K
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// We need our helpers to get to filenames under ROMs or IO area
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jsr install_ram_routines
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#endif
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// Allow platform-specific routine to takeover the flow
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TARGET_HOOK_LOAD()
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// Check whether we support the requested device
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lda FA
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and #$FC
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bne !+
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jmp lvs_illegal_device_number // device number below 4, not an IEC device
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!:
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// Device numbers above 30 are also illegal (see https://www.pagetable.com/?p=1031),
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// as the protocol combines device number with command code int one byte,
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// above 30 it is no longer possible (UNLISTEN and UNTALK codes prevent using
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// number 31), yet original ROMs show ILLEGAL DEVICE NUMBER error only
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// for devices 0-3; in our implementation LISTEN / TALK will cause device
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// not present detected for numbers above 30
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// Display SEARCHING FOR + filename
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jsr lvs_display_searching_for
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// http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
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// p13, 16; also p16 tells us this routine doesn't mess with the file table
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// in the C64, only in the drive.
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// Call device to LISTEN (p16)
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lda FA
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jsr LISTEN
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bcc !+
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jmp lvs_device_not_found_error // XXX deduplicate with other jumps in this routine
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!:
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// Open channel 0 (reserved for file reading)
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lda #$00
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jsr iec_cmd_open
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bcc !+
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jmp lvs_device_not_found_error // XXX deduplicate with other jumps in this routine
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!:
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// Send file name
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jsr lvs_send_file_name
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bcc !+
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jmp lvs_load_verify_error // XXX deduplicate with other jumps in this routine
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!:
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// Now command device to talk (p16)
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lda FA
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jsr TALK
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bcc !+
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jmp lvs_load_verify_error // XXX deduplicate with other jumps in this routine
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!:
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lda #$60 // open channel / data (p3) , required according to p13
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sta TBTCNT
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jsr iec_tx_command
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bcc !+
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jmp lvs_load_verify_error // XXX deduplicate with other jumps in this routine
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!:
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// We are currently talker, so do the IEC turn around so that we
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// are the listener (p16)
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jsr iec_turnaround_to_listen
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bcc !+
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jmp lvs_load_verify_error // XXX deduplicate with other jumps in this routine
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!:
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// Get load address and store it if secondary address is zero
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jsr iec_rx_byte
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bcc !+
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jmp lvs_file_not_found_error // XXX deduplicate with other jumps in this routine
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!:
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ldx SA
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beq !+
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sta STAL+0
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!:
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jsr iec_rx_byte
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bcc !+
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jmp lvs_file_not_found_error // XXX deduplicate with other jumps in this routine
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!:
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ldx SA
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beq !+
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sta STAL+1
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!:
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// Display start address
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jsr lvs_display_loading_verifying
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load_loop:
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// We are now ready to receive bytes
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jsr iec_rx_byte
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bcc !+
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jmp lvs_load_verify_error // XXX deduplicate with other jumps in this routine
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!:
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// Handle the byte (store in memory / verify)
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jsr lvs_handle_byte_load_verify
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bcc !+
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jmp lvs_load_verify_error // XXX deduplicate with other jumps in this routine
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!:
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// Advance pointer to data
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jsr lvs_advance_pointer
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bcc !+
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jmp lvs_wrap_around_error
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!:
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// Check for EOI - if so, this was the last byte
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lda IOSTATUS
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and #K_STS_EOI
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beq load_loop
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// Display end address
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jsr lvs_display_done
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// Close file on drive
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lda FA
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jsr close_load
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// Return last address
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jmp lvs_return_last_address
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