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sms: implement (spix) in z80 asm

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Doing SPI bit-banging through a controller port is already really
slow, but doing so with the Forth version of (spix) was really,
really slow.

With this pure z80 version of (spix), it's more bearable.
This commit is contained in:
Virgil Dupras 2020-11-17 13:41:44 -05:00
parent 4d26f1c490
commit 959382c079
1 changed files with 14 additions and 9 deletions
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23
arch/z80/sms/blk.fs
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@ -151,15 +151,20 @@ TL. When the '164 is full, TL is low. Port A TL is bit 4 )
2 _THB! ( TH input ) ;
( ----- 622 )
: (spie) DROP ; ( always enabled )
: (spix) ( x -- x, for port B )
0 SWAP ( rx tx ) 8 0 DO
( send current bit to TRB, TR's output bit )
DUP 7 I - RSHIFT 1 AND _TRB!
1 _THB! ( CLK hi )
( read into rx ) SWAP 1 LSHIFT _D1@ ( tx rx<< x )
0 _THB! ( CLK lo )
( out bit is the 6th ) 6 RSHIFT 1 AND OR
SWAP LOOP ( rx tx ) DROP ;
CODE (spix) ( x -- x, for port B ) HL POP, chkPS,
( TR = DATA TH = CLK )
CPORT_MEM LDA(i), 0xf3 ANDi, ( TR/TH output )
H 8 LDri, BEGIN,
0xbf ANDi, ( TR lo ) L RL, ( --> C )
IFC, 0x40 ORi, ( TR hi ) THEN,
CPORT_CTL OUTiA, ( clic! ) 0x80 ORi, ( TH hi )
CPORT_CTL OUTiA, ( clac! )
EXAFAF', CPORT_D1 INAi, ( Up Btn is B6 ) RLA, RLA,
E RL, EXAFAF',
0x7f ANDi, ( TH lo ) CPORT_CTL OUTiA, ( cloc! )
H DECr, JRNZ, AGAIN, CPORT_MEM LD(i)A,
L E LDrr, HL PUSH,
;CODE
( ----- 625 )
( Routines for interacting with SMS controller ports.
Requires CPORT_MEM, CPORT_CTL, CPORT_D1 and CPORT_D2 to be