; -----------------------------------------------------------------------------
;  System Clock......
;
;       8 MHz XTAL
;       2 MHZ 'E' clock
;       The main system timers prescaler is set to divide by 4.  This would
;        set its freq to 500 KHz with a period of 2 us.
;       Input into the 6840 time is divided by 8 to 250 KHz (4us)
;
; -----------------------------------------------------------------------------
;  External Timer .......
;
;       SG Thompson EF68B40PV   - Three 16 bit timers
;       Same as EF3840, MC6840, or HD6340
;
;       All the clock inputs are fed with a 250 KHz clock ( E clock / 8)
;       4us per per count
;       All the gates are tied to ground.
;       The are configured in 16 bit Single shot mode...
;
;       Timer #1 (O1) - drives INJ-A (cylinders 1 and 8)
;       Timer #2 (O2) - drives INJ-C (cylinders 4 and 3)
;       Timer #3 (O3) - drives INJ-B (cylinders 6 and 5)
;
;       Addressing:
;               A12 is tied to the CS1
;               A11 - is qualified by the PAL - *CS0
;               A10 - RS2
;                A9 - RS1
;                A8 - RS0
;
;       Address         Write                   Read
;
;        $3000          Control Register #3             0
;                       Control Register #1             0
;        $3100          Control Register #2             Status Register
;                       Control Register #1             0
;        $3100          Control Register #2             Status Register
;        $3200          MSB Buffer Register #1          Timer #1 Counter
;        $3300          Timer #1 Latches                LSB Buffer Register
;        $3400          MSB Buffer Register #2          Timer #2 Counter
;        $3500          Timer #2 Latches                LSB Buffer Register
;        $3600          MSB Buffer Register #3          Timer #3 Counter
;        $3700          Timer #3 Latches                LSB Buffer Register
;
timer_cntr_regx equ     $3000
timer_cntr_reg2 equ     $3100
timer_1_msb     equ     $3200
timer_1_lsb     equ     $3300
timer_2_msb     equ     $3400
timer_2_lsb     equ     $3500
timer_3_msb     equ     $3600
timer_3_lsb     equ     $3700
;
; ---------------------------------------------------------------------------------