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- ; ZuluSCSI™ - Copyright (c) 2022-2025 Rabbit Hole Computing™
- ;
- ; ZuluSCSI™ firmware is licensed under the GPL version 3 or any later version.
- ;
- ; https://www.gnu.org/licenses/gpl-3.0.html
- ; ----
- ; This program is free software: you can redistribute it and/or modify
- ; it under the terms of the GNU General Public License as published by
- ; the Free Software Foundation, either version 3 of the License, or
- ; (at your option) any later version.
- ;
- ; This program is distributed in the hope that it will be useful,
- ; but WITHOUT ANY WARRANTY; without even the implied warranty of
- ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- ; GNU General Public License for more details.
- ;
- ; You should have received a copy of the GNU General Public License
- ; along with this program. If not, see <https://www.gnu.org/licenses/>.
- ; RP2040 PIO program for accelerating SCSI initiator / host function
- ; Run "pioasm scsi_accel_host.pio scsi_accel_host.pio.h" to regenerate the C header from this.
- ; GPIO mapping:
- ; - 0-7: DB0-DB7
- ; - 8: DBP
- ; Side set is ACK pin
- ; REQ is a dummy value, set by via pico-sdk encode functions
- .define REQ 9
- .define ACK 10
- ; Read from SCSI bus using asynchronous handshake.
- ; Data is returned as 16-bit words that contain the 8 data bits + 1 parity bit.
- ; Number of bytes to receive minus 1 should be written to TX fifo.
- ; Number of bytes to receive must be divisible by 2.
- .program scsi_host_async_read
- .side_set 1
- pull block side 1 ; Get number of bytes to receive
- mov x, osr side 1 ; Store to counter X
- start:
- wait 0 gpio REQ side 1 ; Wait for REQ low
- in pins, 9 side 0 ; Assert ACK, read GPIO
- in null, 7 side 0 ; Padding bits
- wait 1 gpio REQ side 0 ; Wait for REQ high
- jmp x-- start side 1 ; Deassert ACK, decrement byte count and jump to start
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