design.txt

MOS-VDP combo
=============
WAKEUP
- MOS sends GP packet for some time
- VDP answers with echo GP packet
VDP sends raw chars to MOS
- only in Terminal mode after set by VDP packet
VDP sends packets to MOS
- packets have high-bit 7 + cmd nr
- followed by length
- followed by bytes
MOS sends packets or chars to VDP
- packets start with CTRL-W
- chars are everything else
    special care for special chars
    case 0x20 ... 0x7E:
	case 0x80 ... 0xFF:
		plotCharacter(c);



ELECTRON HAL - OS combo
========================
WAKEUP
- HAL sends ESC to OS
- OS responds with CTRL-Z
HAL sends raw chars to OS
-bit 7 is low + 7 bits ASCII
HAL sends command to OS
-bit 7 is high + 7 bits cmd-id
-00 = VIRTUAL-KEYCODE + UP:0/DOWN:1
OS sends raw chars to HAL
OS sends commands to HAL
-bit 7 is high + 7 bits cmd-id
-OUTPUT/INPUT/FILL/BLOCKRD/BLOCKWR


SOLVED DIFFERENCES:
===================

MOS - hardware CTS via input pin, no hardware RTS
=================================================
PORTD_DDR = 0000 1011
PORTD_ALT1= 1111 0100
PORTD_ALT2= 0000 0011
RX/TX (pins 0,1) are alternative function => UART
CTS (pin 3) is input
write waits for CTS becoming Z
MCTL = 0 (no and reset RTS)

EOS - hardware CTS and RTS
=================================================
PORTD_DDR = 0000 1111
PORTD_ALT1= 1111 0000
PORTD_ALT2= 0000 1111
RX/TX/CTS/RTS (pins 0,1,2,3) are alternative function => UART
write waits for bit4 MSR becoming NZ
MCTL = 2 (use and set RTS)