mirror of
https://github.com/cc65/cc65.git
synced 2024-11-18 00:07:21 +00:00
413 lines
8.1 KiB
ArmAsm
413 lines
8.1 KiB
ArmAsm
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;
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; Serial driver for the Atari Lynx ComLynx port.
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;
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; Karri Kaksonen, 17.09.2009
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;
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.include "lynx.inc"
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.include "zeropage.inc"
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.include "ser-kernel.inc"
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.include "ser-error.inc"
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; ------------------------------------------------------------------------
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; Header. Includes jump table
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.segment "JUMPTABLE"
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; Driver signature
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.byte $73, $65, $72 ; "ser"
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.byte SER_API_VERSION ; Serial API version number
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; Jump table.
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.addr INSTALL
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.addr UNINSTALL
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.addr OPEN
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.addr CLOSE
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.addr GET
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.addr PUT
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.addr STATUS
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.addr IOCTL
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.addr IRQ
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;----------------------------------------------------------------------------
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; Global variables
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;
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; The ring buffers will be at the fixed place
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; Tx buffer $200 - $2ff. Rx buffer $300 - $3ff.
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; This memory area can usually not be used for anything as the encryption
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; stuff needs it. But for this purpose it fits perfectly.
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.bss
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TxBuffer = $0200
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RxBuffer = $0300
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RxPtrIn: .res 1
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RxPtrOut: .res 1
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TxPtrIn: .res 1
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TxPtrOut: .res 1
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contrl: .res 1
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SerialStat: .res 1
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TxDone: .res 1
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.code
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;----------------------------------------------------------------------------
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; INSTALL: Is called after the driver is loaded into memory.
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;
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; Must return an SER_ERR_xx code in a/x.
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INSTALL:
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; Set up IRQ vector ?
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;----------------------------------------------------------------------------
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; UNINSTALL: Is called before the driver is removed from memory.
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; No return code required (the driver is removed from memory on return).
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;
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UNINSTALL:
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;----------------------------------------------------------------------------
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; CLOSE: Close the port and disable interrupts. Called without parameters.
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; Must return an SER_ERR_xx code in a/x.
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CLOSE:
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; Disable interrupts
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; Done, return an error code
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lda #<SER_ERR_OK
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ldx #>SER_ERR_OK
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rts
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;----------------------------------------------------------------------------
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; OPEN: A pointer to a ser_params structure is passed in ptr1.
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;
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; The Lynx has only two correct serial data formats:
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; 8 bits, parity mark, 1 stop bit
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; 8 bits, parity space, 1 stop bit
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;
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; It also has two wrong formats;
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; 8 bits, even parity, 1 stop bit
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; 8 bits, odd parity, 1 stop bit
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;
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; Unfortunately the parity bit includes itself in the calculation making
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; parity not compatible with the rest of the world.
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;
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; We can only specify a few baud rates.
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; Lynx has two non-standard speeds 31250 and 62500 which are
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; frequently used in games.
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;
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; The receiver will always read the parity and report parity errors.
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;
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; Must return an SER_ERR_xx code in a/x.
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OPEN:
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stz RxPtrIn
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stz RxPtrOut
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stz TxPtrIn
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stz TxPtrOut
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; clock = 8 * 15625
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lda #%00011000
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sta TIM4CTLA
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ldy #SER_PARAMS::BAUDRATE
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lda (ptr1),y
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ldx #1
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cmp #SER_BAUD_62500
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beq setbaudrate
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ldx #2
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cmp #SER_BAUD_31250
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beq setbaudrate
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ldx #12
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cmp #SER_BAUD_9600
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beq setbaudrate
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ldx #25
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cmp #SER_BAUD_4800
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beq setbaudrate
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ldx #51
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cmp #SER_BAUD_2400
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beq setbaudrate
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ldx #103
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cmp #SER_BAUD_1200
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beq setbaudrate
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ldx #207
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cmp #SER_BAUD_600
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beq setbaudrate
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; clock = 6 * 15625
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ldx #%00011010
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stx TIM4CTLA
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ldx #12
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cmp #SER_BAUD_7200
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beq setbaudrate
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ldx #25
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cmp #SER_BAUD_3600
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beq setbaudrate
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ldx #207
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stx TIM4BKUP
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; clock = 4 * 15625
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ldx #%00011100
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cmp #SER_BAUD_300
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beq setprescaler
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; clock = 6 * 15625
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ldx #%00011110
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cmp #SER_BAUD_150
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beq setprescaler
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; clock = 1 * 15625
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ldx #%00011111
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stx TIM4CTLA
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cmp #SER_BAUD_75
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beq baudsuccess
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ldx #141
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cmp #SER_BAUD_110
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beq setbaudrate
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; clock = 2 * 15625
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ldx #%00011010
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stx TIM4CTLA
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ldx #68
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cmp #SER_BAUD_1800
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beq setbaudrate
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; clock = 6 * 15625
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ldx #%00011110
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stx TIM4CTLA
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ldx #231
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cmp #SER_BAUD_134_5
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beq setbaudrate
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lda #<SER_ERR_BAUD_UNAVAIL
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ldx #>SER_ERR_BAUD_UNAVAIL
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rts
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setprescaler:
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stx TIM4CTLA
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bra baudsuccess
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setbaudrate:
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stx TIM4BKUP
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baudsuccess:
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ldx #TxOpenColl|ParEven
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stx contrl
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ldy #SER_PARAMS::DATABITS ; Databits
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lda (ptr1),y
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cmp #SER_BITS_8
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bne invparameter
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ldy #SER_PARAMS::STOPBITS ; Stopbits
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lda (ptr1),y
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cmp #SER_STOP_1
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bne invparameter
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ldy #SER_PARAMS::PARITY ; Parity
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lda (ptr1),y
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cmp #SER_PAR_NONE
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beq invparameter
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cmp #SER_PAR_MARK
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beq checkhs
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cmp #SER_PAR_SPACE
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bne @L0
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ldx #TxOpenColl
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stx contrl
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bra checkhs
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@L0:
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ldx #TxParEnable|TxOpenColl|ParEven
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stx contrl
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cmp #SER_PAR_EVEN
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beq checkhs
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ldx #TxParEnable|TxOpenColl
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stx contrl
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checkhs:
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ldx contrl
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stx SERCTL
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ldy #SER_PARAMS::HANDSHAKE ; Handshake
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lda (ptr1),y
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cmp #SER_HS_NONE
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bne invparameter
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lda SERDAT
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lda contrl
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ora #RxIntEnable|ResetErr
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sta SERCTL
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lda #<SER_ERR_OK
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ldx #>SER_ERR_OK
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rts
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invparameter:
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lda #<SER_ERR_INIT_FAILED
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ldx #>SER_ERR_INIT_FAILED
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rts
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;----------------------------------------------------------------------------
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; GET: Will fetch a character from the receive buffer and store it into the
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; variable pointed to by ptr1. If no data is available, SER_ERR_NO_DATA is
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; returned.
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GET:
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lda RxPtrIn
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cmp RxPtrOut
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bne GetByte
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lda #<SER_ERR_NO_DATA
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ldx #>SER_ERR_NO_DATA
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rts
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GetByte:
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ldy RxPtrOut
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lda RxBuffer,y
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inc RxPtrOut
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ldx #$00
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sta (ptr1,x)
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txa ; Return code = 0
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rts
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;----------------------------------------------------------------------------
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; PUT: Output character in A.
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; Must return an SER_ERR_xx code in a/x.
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PUT:
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tax
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lda TxPtrIn
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ina
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cmp TxPtrOut
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bne PutByte
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lda #<SER_ERR_OVERFLOW
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ldx #>SER_ERR_OVERFLOW
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rts
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PutByte:
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ldy TxPtrIn
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txa
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sta TxBuffer,y
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inc TxPtrIn
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bit TxDone
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bmi @L1
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php
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sei
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lda contrl
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ora #TxIntEnable|ResetErr
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sta SERCTL ; Allow TX-IRQ to hang RX-IRQ
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sta TxDone
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plp
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@L1:
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lda #<SER_ERR_OK
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tax
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rts
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;----------------------------------------------------------------------------
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; STATUS: Return the status in the variable pointed to by ptr1.
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; Must return an SER_ERR_xx code in a/x.
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STATUS:
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ldy SerialStat
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ldx #$00
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sta (ptr1,x)
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txa ; Return code = 0
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rts
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;----------------------------------------------------------------------------
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; IOCTL: Driver defined entry point. The wrapper will pass a pointer to ioctl
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; specific data in ptr1, and the ioctl code in A.
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; Must return an SER_ERR_xx code in a/x.
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IOCTL:
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lda #<SER_ERR_INV_IOCTL
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ldx #>SER_ERR_INV_IOCTL
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rts
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;----------------------------------------------------------------------------
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; IRQ: Called from the builtin runtime IRQ handler as a subroutine. All
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; registers are already saved, no parameters are passed, but the carry flag
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; is clear on entry. The routine must return with carry set if the interrupt
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; was handled, otherwise with carry clear.
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;
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; Both the Tx and Rx interrupts are level sensitive instead of edge sensitive.
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; Due to this bug you have to disable the interrupt before clearing it.
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IRQ:
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lda INTSET ; Poll all pending interrupts
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and #SERIAL_INTERRUPT
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bne @L0
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clc
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rts
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@L0:
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bit TxDone
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bmi @tx_irq ; Transmit in progress
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ldx SERDAT
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lda SERCTL
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and #RxParityErr|RxOverrun|RxFrameErr|RxBreak
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beq @rx_irq
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tsb SerialStat ; Save error condition
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bit #RxBreak
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beq @noBreak
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stz TxPtrIn ; Break received - drop buffers
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stz TxPtrOut
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stz RxPtrIn
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stz RxPtrOut
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@noBreak:
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lda contrl
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ora #RxIntEnable|ResetErr
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sta SERCTL
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lda #$10
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sta INTRST
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bra @IRQexit
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@rx_irq:
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lda contrl
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ora #RxIntEnable|ResetErr
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sta SERCTL
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txa
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ldx RxPtrIn
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sta RxBuffer,x
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txa
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inx
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@cont0:
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cpx RxPtrOut
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beq @1
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stx RxPtrIn
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lda #SERIAL_INTERRUPT
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sta INTRST
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bra @IRQexit
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@1:
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sta RxPtrIn
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lda #$80
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tsb SerialStat
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@tx_irq:
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ldx TxPtrOut ; Has all bytes been sent?
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cpx TxPtrIn
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beq @allSent
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lda TxBuffer,x ; Send next byte
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sta SERDAT
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inc TxPtrOut
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@exit1:
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lda contrl
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ora #TxIntEnable|ResetErr
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sta SERCTL
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lda #SERIAL_INTERRUPT
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sta INTRST
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bra @IRQexit
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@allSent:
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lda SERCTL ; All bytes sent
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bit #TxEmpty
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beq @exit1
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bvs @exit1
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stz TxDone
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lda contrl
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ora #RxIntEnable|ResetErr
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sta SERCTL
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lda #SERIAL_INTERRUPT
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sta INTRST
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@IRQexit:
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clc
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rts
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