shell: add input routine

This commit is contained in:
Virgil Dupras 2019-04-12 21:28:50 -04:00
parent 89e4edfa52
commit 358c551bcc
2 changed files with 112 additions and 8 deletions

View File

@ -1,5 +1,7 @@
; classic RC2014 setup (8K ROM + 32K RAM) and a stock Serial I/O module
RAMEND .equ 0xa000
; The RAM module is selected on A15, so it has the range 0x8000-0xffff
RAMSTART .equ 0x8000
RAMEND .equ 0xffff
ACIA_CTL .equ 0x80 ; Control and status. RS off.
ACIA_IO .equ 0x81 ; Transmit. RS on.

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@ -2,8 +2,9 @@
;
; Runs a shell over an asynchronous communication interface adapter (ACIA).
; *** STATUS ***
; Incomplete. This just outputs the welcome prompt then halts
; Incomplete. For now, this outputs a welcome prompt and then waits for input.
; Whenever input is CR or LF, we echo back what we've received and empty the
; input buffer. This also happen when the buffer is full.
#include "platform.inc"
@ -11,28 +12,50 @@
CR .equ 0x0d
LF .equ 0x0a
; size of the input buffer. If our input goes over this size, we echo
; immediately.
BUFSIZE .equ 0x20
; *** VARIABLES ***
; Our input buffer starts there
INPTBUF .equ RAMSTART
; index, in the buffer, where our next character will go. 0 when the buffer is
; empty, BUFSIZE-1 when it's almost full.
BUFIDX .equ INPTBUF+BUFSIZE
; *** CODE ***
jr init
init:
di ; no need for interrupts yet
; disable interrupts we don't need them
di
; setup stack
ld hl, RAMEND
ld sp, hl
; initialize variables
xor a
ld (BUFIDX), a ; starts at 0
; setup ACIA
; CR7 (1) - Receive Interrupt enabled
; CR7 (1) - Receive Interrupt disabled
; 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
ld a, 0b00010110
out (ACIA_CTL), a
; print prompt
ld hl, d_welcome
call printstr
halt
call printcrlf
mainloop:
call readc
call chkbuf
jr mainloop
; spits character in A in port SER_OUT
printc:
@ -55,5 +78,84 @@ printstr:
jr printstr
; no ret because our only way out is ret z above
printcrlf:
ld a, CR
call printc
ld a, LF
call printc
ret
; wait until a char is read in the ACIA and put it in the read buffer
readc:
; first thing first: is our input buffer full? If yes, we don't even
; bother reading the ACIA. Something is wrong: we don't process data
; fast enough.
ld a, (BUFIDX)
cp BUFSIZE
ret z ; if BUFIDX == BUFSIZE, our buffer is full.
call getbufptr
; increase our buf ptr while we still have it in A
inc a
ld (BUFIDX), a
.loop:
; Read our character from ACIA into our BUFIDX
in a, (ACIA_CTL)
bit 0, a ; is our ACIA rcv buffer full?
jr z, .loop ; no? loop
in a, (ACIA_IO)
ld (hl), a
ret
; check if the input buffer is full or ends in CR or LF. If it does, prints it
; back and empty it.
chkbuf:
ld a, (BUFIDX)
cp 0
ret z ; BUFIDX is zero? nothing to check.
cp BUFSIZE
jr z, .do ; if BUFIDX == BUFSIZE? do!
call getbufptr
; our previous char is in BUFIDX - 1. Fetch this
dec hl
ld a, (hl) ; now, that's our char we have in A
inc hl ; put HL back where it was
cp CR
jr z, .do ; char is CR? do!
cp LF
jr z, .do ; char is LF? do!
; nothing matched? don't do anything
ret
.do:
; terminate our string with 0
xor a
ld (hl), a
; reset buffer index
ld (BUFIDX), a
; alright, let's go!
ld hl, INPTBUF
call printstr
call printcrlf
ret
; Set current buffer pointer in HL. The buffer pointer is where our *next* char
; will be written.
getbufptr:
ld hl, INPTBUF
xor b
ld c, a
add hl, bc ; hl now points to INPTBUF + BUFIDX
ret
; *** DATA ***
d_welcome: .byte "Welcome to Collapse OS", CR, LF, 0
d_welcome: .byte "Welcome to Collapse OS", 0