EM6517 ETC, EM6517 Datasheet - Page 27

• Manufacturer Part Number: EM6517
• Description: 4 BIT MICROCONTROLLER
• Manufacturer: ETC

8.6 Counter Setup
RegCDataL[3:0],
CReg[9:0] which is written into the count register bits Count[9:0] when writing the bit Load to ‘1’ in RegCCntl2.
This bit is automatically reset thereafter. The counter value Count[9:0] can be read out at any time, except
when using non-debounced high frequency port A input clock. To maintain data integrity the lower nibble
Count[3:0] must always be read first. The ShCount[9:4] values are shadow registers to the counter. To keep
the data integrity during a counter read operation (3 reads), the counter values [9:4] are copied into these
registers with the read of the count[3:0] register. If using non-debounced high frequency port A input the counter
must be stopped while reading the Count[3:0] value to maintain the data integrity.
In down count mode an interrupt request IRQCount0 is generated when the counter reaches 0. In up count
mode, an interrupt request is generated when the counter reaches 3FF (or FF,3F,F if limited bit counting).
Never an interrupt request is generated by loading a value into the counter register.
When the counter is programmed from up into down mode or vice versa, the counter value Count[9:0] gets
inverted. As a consequence, the initial value of the counter must be programmed after the Up/Down selection.
Loading the counter with hex 000 is equivalent to writing stop mode, the Start bit is reset, no interrupt request is
generated.
How to use the counter;
8.7 10-bit Counter Registers
Table 8.7.1 Register RegCCntl1
Table 8.7.2 Counter Input Frequency Selection with CountFSel[2..0]
Bit
CountFSel2
3
2
1
0
If PWM output is required one has to put the port B[3] in output mode and set PWMOn=1 in step 5.
1st,
2nd,
3rd,
4th,
6th,
7th,
Default : PA0 ,selected as input clock, Down counting
5th,
0
0
0
0
1
1
1
1
set the counter into stop mode (Start=0).
select the frequency and up- or down count mode in RegCCntl1.
if compare mode desired , then write RegCDataL, RegCDataM, RegCDataH (compare value)
set bit Start and select EnComp in RegCCntl2
write the data registers RegCDataL, RegCDataM, RegCDataH (counter start value and length)
load the counter, Load=1, and choose the mode. (EvCount, EnComp=0)
select bits PWMOn in RegPresc and SelIntFull in RegSysCntl1
CountFSel2
CountFSel1
CountFsel0
Up/Down
RegCDataM[3:0], RegCDataH[1:0] are used to store the initial count value called
Name
FOR ENGINEERING ONLY
CountFSel1
0
0
1
1
0
0
1
1
Reset
0
0
0
0
R/W
R/W
R/W
R/W
R/W
CountFSel0
0
1
0
1
0
1
0
1
Up or down counting
Input clock selection
Input clock selection
Input clock selection
clock source selection
Description
© EM Microelectronic-Marin SA, 09/99, Rev. A/277
Prescaler Ck[10]
Prescaler Ck[15]
Prescaler Ck[12]
Prescaler Ck[8]
Prescaler Ck[4]
Prescaler Ck[1]
Port A
Port A
EM6517
PA[0]
PA[3]
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