Accessing output pins in joystick ports

;****************************************
; SPI for MSX *
;****************************************
; MISO ->: Up (Joy-1pin) PA/0
; VDD <-: +5V (Joy-5pin)
; MOSI <-: TrgA (Joy-6pin) PB/0 | PB/2
; SCK <-: TrgB (Joy-7pin) PB/1 | PB/3
; RESET <-: STROBE (Joy-8pin) PB/4 | PB/5
; GND : GND (Joy-9pin)
;----------
; SEL 1|2 : PB/6=0|PB/6=1
;----------------------------------------
PUBLIC set_j1,set_j2,res_joy
PUBLIC imp_SCK,clr_SCK
PUBLIC pas_RES,act_RES
PUBLIC rdser,wrser
.z80
;****************************************
PSG_A equ 0a0h ;reg address
PSG_W equ 0a1h ;reg data WR
PSG_R equ 0a2h ;reg data RD
;========================================
; Set port Joy 1
set_j1: ld a,15 ;address PORT B
out (PSG_A),a
in a,(PSG_R) ;RD port B
ld (JOY_S0),a ; save
and 08fh ;SEL=0 (PB/6=0)
;RESET=0 (PB/4,5=0)
or 00fh ;MOSI=1,SCK=1
jr ini_set
;========================================
; Set port Joy 2
set_j2: ld a,15 ;address PORT B
out (PSG_A),a
in a,(PSG_R)
ld (JOY_S0),a
and 0cfh ;RESET=0 (PB/4,5=0)
or 04fh ;SEL=1,MOSI=1,SCK=1
ini_setut (PSG_W),a ;write in B
ld (JOY_S1),a ; save code
ret
;------------------------------------------------
; restore ports
res_joy:ld a,15 ;порт B
out (PSG_A),a ;
ld a,(JOY_S0)
out (PSG_W),a
ret
;--------------------------------------------------
JOY_S0: db 0
JOY_S1: db 0
;==================================================
;*** SCK = 0 (PB/3,1=0)
clr_sck:ld a,15 ;port B
out (PSG_A),a
ld a,(JOY_S1)
jr ini2
;--------------------------------------------------
; SCK _/~\_ (PB/3,1)
imp_sck:ld a,15 ;port B
out (PSG_A),a
ld a,(JOY_S1)
or 08h OR 02h ;SCK = 1 (TRGB2=H)
; ; (TRGB1=H)
out (PSG_W),a
ini2: and 0f7h AND 0fdh ;SCK = 0 (TRGB2=L)
; ; (TRGB1=L)
out (PSG_W),a
or 04h OR 01h ;MOSI =1 (TRGA2=H)
; (TRGA1=H)
ld (JOY_S1),a
ret
;--------------------------------------------------
;*** RESET control (PB/4,5)
pas_res:ld a,15 ;port B
out (PSG_A),a
ld a,(JOY_S1)
or 30h ;RESET=1 (STB=1)
jr pa_res
;--------------------------------------------------
act_res:ld a,15 ;port B
out (PSG_A),a
ld a,(JOY_S1)
and 0cfh ;RESET=0(STB=0)
pa_res: out (PSG_W),a
ld (JOY_S1),a
ret
;==================================================
; receive byte [result -> (C)]
rdser: ld c,0 ;send byte = 0
; send byte from (C)
wrser: ld b,8 ;counter bits
ld a,15 ;port B
out (PSG_A),a
;/---- Cycle of reception and transfer of byte ----\
wrckl:
;----
ld a,(JOY_S1) ;MOSI = H
rl c ;CY <- data_out(7)
jr c,wr_cy
and 0fbh AND 0feh ;MOSI = L (TRGA2=L)
; (TRGA1=L)
wr_cy: out (PSG_W),a ;
ld (JOY_S1),a
;----
ld a,14 ;port A
out (PSG_A),a
in a,(PSG_R) ;RD port A
push af
call imp_SCK ; SCK _/~\_
pop af
rra ;data_in -> CY
djnz wrckl ; To repeat 8 time
;
rl c ; (C) result
ret
;=================================
end

I think I am not yet ready for assembler but I will try to write those pins in basic using the ports. One more question (maybe dumb): once I set to High a pin ¿how long does it stay in this status?

Thanks again. As mentioned above I want to use it with an arduino board. I have realized that there is a library for arduino that implements SPI protocol. http://arduino.cc/en/Reference/SPI
Wiring schema

I think arduino can be perfectly wired with the pin reference on top of your code and should work. If you can give me your opinion would be great.

So as a newbie I should generate a binary from your assembler code, load it into memory and call the routines from basic. Let's imagine I am able to reach this point :) : Could you give a basic example of how to call and use this library to send and receive data?

Thanks caro

OK, now I know how to call assembly code from basic, it is fairly easy. So I just need to know the purpose of the PUBLIC routines:

PUBLIC set_j1,set_j2: Seems evident, wich joy we want to use for the transfer
PUBLIC res_joy: ¿Reset joystick? OK. When?
PUBLIC imp_SCK,clr_SCK: ¿?
PUBLIC pas_RES,act_RES: ¿Passive , Active?
PUBLIC rdser,wrser: Reas, write byte

How do I use imp_SCK,clr_SCK?