Rainbow Electronics ATAR862-3 - Manual (Page 52)

52
ATAR862-3
4556B–4BMCU–02/03
Timer 2 Mode Register 2
(T2M2) Address: "7"hex - Subaddress: "2"hex
If one of these output modes is used the T2O alternate function of Port 4 must also be
activated.
Timer 2 Compare and
Compare Mode Registers Timer 2 has two separate compare registers, T2CO1 for the 4-bit stage and T2CO2 for
the 8-bit stage of Timer 2. The timer compares the contents of the compare register cur-
rent counter value and if it matches it generates an output signal. Dependent on the
timer mode, this signal is used to generate a timer interrupt, to toggle the output flip-flop
as SSI clock or as a clock for the next counter stage.
In the 12-bit timer mode, T2CO1 contains bits 0 to 3 and T2CO2 bits 4 to 11 of the 12-bit
compare value. In all other modes, the two compare registers work independently as a
4- and 8-bit compare register.
When asigned to the compare register a compare event will be suppressed.
Bit 3 Bit 2 Bit 1 Bit 0
T2TOP T2OS2 T2OS1 T2OS0 Reset value: 1111b
T2TOP T imer 2 T oggle O utput P reset
This bit allows the programmer to preset the Timer 2 output T2O.
T2TOP = 0, resets the toggle outputs with the write cycle (M2 = 0)
T2TOP = 1, sets toggle outputs with the write cycle (M2 = 1)
Note: If T2R = 1, no output preset is possible
T2OS2 T imer 2 O utput S elect bit 2
T2OS1 T imer 2 O utput S elect bit 1
T2OS0 T imer 2 O utput S elect bit 0
Output
Mode T2OS2 T2OS1 T2OS0 Clock Output (POUT)
1 1 1 1 Toggle mode: a Timer 2 compare match toggles
the output flip-flop (M2) -> T2O
2 1 1 0 Duty cycle burst generator 1: the DCG output
signal (DCG0) is given to the output and gated by
the output flip-flop (M2)
3 1 0 1 Duty cycle burst generator 2: the DCG output
signal (DCGO) is given to the output and gated by
the SSI internal data output (SO)
4 1 0 0 Biphase modulator: Timer 2 modulates the SSI
internal data output (SO) to Biphase code
5 0 1 1 Manchester modulator: Timer 2 modulates the SSI
internal data output (SO) to Manchester code
6 0 1 0 SSI output: T2O is used directly as SSI internal
data output (SO)
7 0 0 1 PWM mode: an 8/12-bit PWM mode
8 0 0 0 Not allowed