2019-04-13 05:16:12 +10:00
|
|
|
; shell
|
|
|
|
|
;
|
|
|
|
|
; Runs a shell over an asynchronous communication interface adapter (ACIA).
|
|
|
|
|
|
|
|
|
|
; *** STATUS ***
|
|
|
|
|
; Incomplete. This just outputs the welcome prompt then halts
|
|
|
|
|
|
2019-04-13 05:53:05 +10:00
|
|
|
#include "platform.inc"
|
2019-04-13 05:16:12 +10:00
|
|
|
|
|
|
|
|
; *** CONSTS ***
|
|
|
|
|
CR .equ 0x0d
|
|
|
|
|
LF .equ 0x0a
|
|
|
|
|
|
|
|
|
|
; *** CODE ***
|
|
|
|
|
jr init
|
|
|
|
|
|
|
|
|
|
init:
|
|
|
|
|
di ; no need for interrupts yet
|
|
|
|
|
|
|
|
|
|
; setup stack
|
|
|
|
|
ld hl, RAMEND
|
|
|
|
|
ld sp, hl
|
|
|
|
|
|
|
|
|
|
; setup ACIA
|
|
|
|
|
; CR7 (1) - Receive Interrupt enabled
|
|
|
|
|
; CR6:5 (00) - RTS low, transmit interrupt disabled.
|
|
|
|
|
; CR4:2 (101) - 8 bits + 1 stop bit
|
|
|
|
|
; CR1:0 (10) - Counter divide: 64
|
|
|
|
|
ld a, 0b10010110
|
|
|
|
|
out (ACIA_CTL), a
|
|
|
|
|
|
|
|
|
|
; print prompt
|
|
|
|
|
ld hl, d_welcome
|
|
|
|
|
call printstr
|
|
|
|
|
halt
|
|
|
|
|
|
|
|
|
|
; spits character in A in port SER_OUT
|
|
|
|
|
printc:
|
|
|
|
|
push af
|
|
|
|
|
.stwait:
|
|
|
|
|
in a, (ACIA_CTL) ; get status byte from SER
|
|
|
|
|
bit 1, a ; are we still transmitting?
|
|
|
|
|
jr z, .stwait ; if yes, wait until we aren't
|
|
|
|
|
pop af
|
|
|
|
|
out (ACIA_IO), a ; push current char
|
|
|
|
|
ret
|
|
|
|
|
|
|
|
|
|
; print null-terminated string pointed to by HL
|
|
|
|
|
printstr:
|
|
|
|
|
ld a, (hl) ; load character to send
|
|
|
|
|
or a ; is it zero?
|
|
|
|
|
ret z ; if yes, we're finished
|
|
|
|
|
call printc
|
|
|
|
|
inc hl
|
|
|
|
|
jr printstr
|
|
|
|
|
; no ret because our only way out is ret z above
|
|
|
|
|
|
|
|
|
|
; *** DATA ***
|
|
|
|
|
d_welcome: .byte "Welcome to Collapse OS", CR, LF, 0
|
