; *** Register rules ***
; Dedicated registers:
; r15 -- A23..A16 for external IO
; r14 -- A15..A8  for external IO

; r9  -- Current character for UART
; r5 -- Menu selection value

; General purpose registers:
; r10, r8, r7, r6 -- Return values for number conversion
; r4 -- Parameter value
; r23, r22, r21, r20, r19, r18, r12, r11, r3, r2, r1, r0 -- Temporary values
; Open: r31, r26, r25, r24, r13








;================
; ROUTINES
; the user input (a character from the hyperterminal)
; is matched to a function
get_char:
  movi r15,UART
  import r5, REG_UART_DATA ; Read from UART
  cmpi r5, 'm'
  bz display_menu
  cmpi r5, 't'
  callz read_uptime
  cmpi r5, 'r'
  callz read_switches
  cmpi r5, '0'
  callz write_led
  cmpi r5, '1'
  callz write_led
  cmpi r5, '2'
  callz write_led
  cmpi r5, '3'
  callz write_led
  cmpi r5, '4'
  callz write_led
  cmpi r5, '5'
  callz write_led
  cmpi r5, '6'
  callz write_led
  cmpi r5, '7'
  callz write_led
  cmpi r5, '8'
  callz write_led
  cmpi r5, '9'
  callz write_led

  call new_prompt
  ret



write_led:                        

  movi r9, ' '
  call send_uart_data
  movi r9, ' '
  call send_uart_data

  ;echo the BCD character to Hyperterminal
  mov r9, r5
  call send_uart_data

  movi r15, LED_SW
  xori r5, 0xFF
  export r5, 0x00

  ret



; read data from dip-switches and tx
; to hyperterminal
read_switches:
  movi r15, LED_SW
  import r4, 0x00
  ;call send_crlf
  call wait_for_uart_txrdy
  movi r9, ' '
  call send_uart_data
  movi r9, ' '
  call send_uart_data
  movi r9, 'S'
  call send_uart_data
  movi r9, 'W'
  call send_uart_data
  movi r9, ':'
  call send_uart_data
  call int2asc   ; takes r4 and converts to hex nibbles in r8,r7 -- eg 0x4A => '4', 'A'
  movi r9, '0'
  call send_uart_data
  movi r9, 'x'
  call send_uart_data
  mov r9, r8
  call send_uart_data
  mov r9, r7
  call send_uart_data
  setz
  ret


read_uptime:
  movi r15, TIMER
  export r0, 0x00  ;; issue a 'write' to latch the current time value
  import r4, 0x02  ;; hour byte of latched time value
  call wait_for_uart_txrdy
  movi r9, ' '
  call send_uart_data
  movi r9, ' '
  call send_uart_data
  movi r9, 'U'
  call send_uart_data
  movi r9, 'p'
  call send_uart_data
  movi r9, 't'
  call send_uart_data
  movi r9, 'i'
  call send_uart_data
  movi r9, 'm'
  call send_uart_data
  movi r9, 'e'
  call send_uart_data
  movi r9, ':'
  call send_uart_data
  movi r9, ' '
  call send_uart_data
  call int2asc10   ; takes r4 and converts to BCD in r8,r7,r6
  mov r9, r8
  call send_uart_data
  mov r9, r7
  call send_uart_data
  mov r9, r6
  call send_uart_data
  movi r9, 'h'
  call send_uart_data
  movi r15, TIMER
  import r4, 0x01  ;; minute byte of time of latched time value
  call int2asc10   ; takes r4 and converts to BCD in r8,r7,r6
  mov r9, r7
  call send_uart_data
  mov r9, r6
  call send_uart_data
  movi r9, 'm'
  call send_uart_data
  movi r15, TIMER
  import r4, 0x00  ;; seconds byte of time of latched time value
  call int2asc10   ; takes r4 and converts to BCD in r8,r7,r6
  mov r9, r7
  call send_uart_data
  mov r9, r6
  call send_uart_data
  movi r9, 's'
  call send_uart_data
  setz
  ret




int2asc10:
  ; input in r4
  ; outputs to r8(100's), r7(10's), r6(1's)
  mov  r6, r4
  movi r7, 0x00 ; tens
  movi r8, 0x00 ; hundreds

  compare_10:
  cmpi r6, 10
  bnc incr_tens
  b bcd_done

  incr_tens:
    subi r6, 10
    addi r7, 1
    cmpi r7, 10
    bz incr_hundreds
    b compare_10

  incr_hundreds:
    addi r8, 1
    movi r7, 0
    b compare_10

  bcd_done:
    addi r6, 0x30
    addi r7, 0x30
    addi r8, 0x30
  ret


int2asc:
  ; input in r4
  ; outputs to r8 (MS-Nibble), r7 (LS-Nibble)
  mov r7, r4
  mov r8, r4
  andi r7, 0x0F
  andi r8, 0xF0
  ror r8, r8
  ror r8, r8
  ror r8, r8
  ror r8, r8
  cmpi r7, 0x0A
  bnc r7_is_alpha
  addi r7, 0x30

  conv_r8:
  cmpi r8, 0x0A
  bnc r8_is_alpha
  addi r8, 0x30
  b int2asc_done
  r7_is_alpha:
  addi r7, 0x37
  b conv_r8
  r8_is_alpha:
  addi r8, 0x37
  int2asc_done:
  ret