EM6520 EM Microelectronic, EM6520 Datasheet - Page 21

• Manufacturer Part Number: EM6520
• Description: MFP version of EM6620 Ultra Low Power Microcontroller 4x8 LCD Driver
• Manufacturer: EM Microelectronic

7
The EM6520 has a built-in universal cyclic counter. It can be configured as 10, 8, 6 or 4-bit counter. If 10-bits
are selected we call that full bit counting, if 8, 6 or 4-bits are selected we call that limited bit counting.
The counter works in up- or down count mode. Eight clocks can be used as the input clock source, six of them
are prescaler frequencies and two are coming from the input pads PA[0] and PA[3]. In this case the counter can
be used as an event counter.
The counter generates an interrupt request IRQCount0 every time it reaches 0 in down count mode or 3FF in
up count mode. Another interrupt request IRQCntComp is generated in compare mode whenever the counter
value matches the compare data register value. Each of this interrupt requests can be masked (default). See
section 9 for more information about the interrupt handling.
A 10-bit data register CReg[9:0] is used to initialize the counter at a specific value (load into Count[9:0] ). This
data register ( CReg[9:0] ) is also used to compare its value against Count[9:0] for equivalence.
A Pulse-Width-Modulation signal (PWM) can be generated and output on port B terminal PB[3].
7.1 Full and Limited Bit Counting
In Full Bit Counting mode the counter uses its maximum
of 10-bits length (default ). With the BitSel[1,0] bits in
register RegCDataH one can lower the counter length,
for IRQ generation, to 8, 6 or 4 bits. This means that
actually the counter always uses all the 10-bits, but
IRQCount0 generation is only performed on the number
of selected bits. The unused counter bits may or may not
be taken into account for the IRQComp generation depending on bit SelIntFull . Refer to chapter 7.4.
Copyright  2002, EM Microelectronic-Marin SA
Figure 13. 10-bit Counter Block Diagram
10-bit Counter
RegCCntl1, 2
CountFSel2...0
Up/Down
Start
EvCount
Load
EnComp
PA[0]
Ck[15]
Ck[12]
Ck[10]
Ck[8]
Ck[4]
Ck[1]
PA[3]
MUX
ck
DB[3:0]
En
ck
Up/Down
En
EvCount
Load
RegCDataL, M, H (CReg[9:0])
21
Table 6.6.1. Counter length selection
Data Register
Counter Read Register
BitSel[1]
Comparator
Up/Down Counter
0
0
1
1
RegCDataL, M, H
(Count[9:0])
BitSel[0 ]
0
1
0
1
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EM6520
counter length
IRQCntComp
10-Bit
IRQCount0
8-Bit
6-Bit
4-Bit
PWM
03/02 REV. D/449