CLOCK-IC (MSX2)

        The CLOCK-IC has 4 blocks,each one consisting of 13 sets of 4-bit
registers (addresses 0 to 12). There are 3 aditional 4-bit registers to select
blocks or control functions (addresses 13 to 15). The registers inside the
block (0 to 12) and the MODE register (13) can be read from/written to. The
TEST (14) and RESET (15) registers can only be written to.

 BLOCK          REGISTER        FUNCTION
   0               0            second(1st digit)
(CLOCK)            1            second(2nd digit)
                   2            minute
                   3            minute
                   4            hour
                   5            hour
                   6            day of the week
                   7            day
                   8            day
                   9            month
                  10            month
                  11            year
                  12            year

 BLOCK          REGISTER        FUNCTION
   1               0            -
(ALARM)            1            -
                   2            minute
                   3            minute
                   4            hour
                   5            hour
                   6            day of the week
                   7            day
                   8            day
                   9            -
                  10            12h or 24h clock
                  11            leap year counter
                  12            -

 BLOCK          REGISTER        bit1    bit2    bit3    bit4
   2               0            id +++++++++++++++++++++++++
                   1            adjust X +++++++++++++++++++
                   2            adjust Y +++++++++++++++++++
                   3            |------|-------|interlc|screen|
                   4            width (low) ++++++++++++++++
                   5            width (high) +++++++++++++++
                   6            foreground color
                   7            background color
                   8            border color
                   9            |cas sp|printer|click |key on/off|
                  10            |BEEP tone     |BEEP volume      |
                  11            |--------------|title color      |
                  12            native code ++++++++++++++++


 BLOCK          REGISTER        id = 0          id = 1          id=2
   3               0            0               1               2
                   1            title           usage id = 1    BASIC prompt
                   2            "               usage id = 2    "
                   3            "               usage id = 3    "
                   4            "               password        "
                   5            "               (compressed in  "
                   6            "               4x4 bits)       "
                   7            "               "               "
                   8            "               key cartr. flag "
                   9            "               key cart. value "
                  10            "               "               "
                  11            "               "               "
                  12            "               "               "
                                
Routines to access to the Clock-IC:

REDCLK (01F5H/SUB-ROM) - read Clock-IC data
Input:  C : address ( . . b5 b4 b3 b2 b1 b0
                          |-+-| |---------|
                            |     register
                            |
                            +---> block

Output: A : data (only 4 lower bits valid)

WRTCLK (01F9H/SUB-ROM) - write Clock-IC data
Input:  C : address
        A : data