/*

SLdt  240809          Disclaimer: none. Sue me.

ATmega162 (8515): external RAM per Software
https://www.mikrocontroller.net/topic/570080#new

Adresse in XH,XL
Daten in data

avrasm2
*/

.def	data	= r18

ext_init:
    ldi     tmp0,$FF
    out     DDRC,tmp0                                   ; address high byte
    cbi     PORTE,1
    sbi     DDRE,1                                      ; ALE
    sbi     PORTD,7
    sbi     DDRD,7                                      ; /RD
    sbi     PORTD,6
    sbi     DDRD,6                                      ; /WR
    ret
;----------------------

ext_write:              ; data -> (x)
    rcall   ext_addr_set
    out     PORTA,data
    cbi     PORTD,6                                     ; /WR
    sbi     PORTD,6
    ret
;----------------------

ext_read:               ; data <- (x)
    rcall   ext_addr_set
    ldi     tmp0,$00
    out     DDRA,tmp0
    cbi     PORTD,7                                     ; /RD
    sbi     PORTD,7
    in      data,PINA
    ret
;----------------------

ext_addr_set:           ; x
    out     PORTC,XH
    ldi     tmp0,$FF
    out     DDRA,tmp0
    out     PORTA,XL
    sbi     PORTE,1                                     ; ALE
    cbi     PORTE,1
    ret