IZ7008
quency forming in timer 2) and "short" pulses FrT2, FrT3 setting respectively interrupt request flag
FR2 into 1 (bit 5 of the state register R7) and Interrupt request flag FR3 in the states register R7
(bit 6 of the state register R7) are formed.
Flag FR2 is not set into mode of notes frequency forming in timer T2 and in mode when
"short" pulse FrT2 of timer T2 clearing is input signal of timer T3.
The timers are controlled by timers control register RFBO (address 0x7D8)
Description of RFBO control register bits:
Bit
Symbol
Description
After
reset
RFBO_7
IN1-T3
7,6 bits choose source of timer T3 input signal
00 – signal of ripple-through carry of timer T1
0
(«short» pulse FrT1)
01 – output Т1_3 of timer Т1 (2048Hz)
10 – signal of clearing timer Т2
RFBO_6
RFBO_5
IN0-T3
IN1-T2
(«short» pulse FrT2), in this mode setting of flag FR2 is inhibited
11 – external signal IN6 (output 06 when disconnecting SEG 01 by mask)
5,4 bits choose source of timer T2 input signal
0
0
00 – signal of ripple-through carry of timer Т1
(«short» pulse FrT1)
01 – output Т1_3 of timer Т1 (2048Hz)
10 – signal 65565 Hz (notes frequency forming mode), in this mode setting of FR2 flag
is inhibited
RFBO_4
RFBO_3
IN0-T2
0
0
11 –external signal IN6, IN7, IN8 (from outputs 06, 07 or 08 when disconnecting corre-
sponding SEG 01, SEG 02, SEG 03 by mask)
CLR-T3
1-clearing (reset and zero code fixation) of T3 timer counter, reset of FR3 flag
(except mode, when T3 is clocked by FrТ2 signal; in this mode RFBO_3 and RFBO_1
shoose source of input signal Т2: 00-IN7, 01-IN6 ,1X –IN8)
1-clearing (reset and zero code fixation) of T2 timer counter, reset of FR2 flag and T3
timer with reset of FR3 flag (when T3 is clocked by FrТ2 signal)
1/0- (count enable) /(count inhibit) Т3 (except mode when Т3 is clocked by FrТ2 signal;
in this mode RFBO_3 and RFBO_1 shoose source of input signal Т2: 00-IN7, 01-IN6
,1X –IN8))
RFBO_2
RFBO_1
CLR-T2
EN-T3
0
0
RFBO_0
EN-T2
1/0- (count enable) / (count inhibit) Т2 (always) and (count enable) / (count inhibit) Т3
(when T3 is clocked by FrТ2 signal )
0
Timer Т2 can be used in the mode of notes frequency forming for tunes synthesis. The
mode is selected when recording code «10» into 5,4 bits of RFBO control register (IN1-T2=1, IN0-
T2 = 0 ) and timer count enabling.
RFBO_7
IN1-T3
RFBO_6
IN0-T3
RFBO_5
IN1-T2
RFBO_4
IN0-T2
RFBO_3
CLR-T3
RFBO_2
CLR-T2
RFBO_1
EN-T3
RFBO_0
EN-T2
X
X
1
0
X
0
X
1
In this mode setting of interrupt request flag FR2 in the state register R7 is inhibited. Signal of
65565 Hz is applied on counter input.. Notes frequency is formed on counter output (output
T2_7) and can be applied on external output "AL" at the set into 1 flag AL_EN in the state
register R7.
Seven lower counter bits count in the beginning of zero semi-period of note. After reaching
the code equal to the contents of 7 lower bits of KT2 register, 7 lower bits of the counter are
cleared but the highest bit is switched into logic 1 and then the note second (unit) semi-
period is counted in the same way.
As a result on output the frequency of 65565Hz/2N is formed, where N is number from 2 to
127, set in 7 lower bits of register KT2. To form notes period with accuracy to one period of
input frequency 65565 Hz the following possibility is forseen. When setting in register KT2
the higher bit of KT register in logic 1 when counting the second (unit) semi-period at code
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