Table 15-5 Output Data Rate Equations - Motorola DragonBall MC9328MX1 Reference Manual

Analog Signal Processor (ASP)
• IDLECNT (t3)—Idle count: This controls the idle time after each set of measurement. During the
idle time, all touch panel control switches are turned off, hence saving current consumption by the
touch panel.
For channels X and Y, DSCNT must be at least 1 to allow sufficient settling
time of the touch panel and the MUX.
MOD AZE
01 0
01 1
10 0
10 1
11 X
The best value for the analog clock ACLK is 12 MHz, which can be controlled by the PADC_CLK field of
the Clock Divide Register. The decimation ratio of the filter is 1260, therefore fclk = ACLK/1260. When
ACLK = 12 MHz, fclk will be 9.6 kHz.
Some examples are provided to illustrate how to calculate the output data rate:
1. If MOD [1:0] = 01 and AZE = 0, the X and Y channels are selected and the auto-zero
measurement is disabled. The maximum output data rate for each channel is 2.4 kHz when
DSCNT = 1, DMCNT = 0 and IDLECNT = 0.
To get a 200Hz output data rate, set DSCNT = 1, DMCNT = 0, and IDLECNT = 44
2. If MOD [1:0] = 10 and AZE = 1, all the channels are selected, with auto-zero measurement
enabled. Maximum output data rate for each channel is 1.2 kHz when DSCNT = 1,
DMCNT = 0 and IDLECNT = 0.
To get a 200Hz output data rate, set DSCNT = 1, DMCNT = 7 (for example, if the
decimation ratio = 8, and IDLECNT = 12.
3. If MOD [1:0] = 11, only U channel is selected and the AZE bit is ignored. Maximum output
data rate is 9.6 kHz when DMCNT = 0 and IDLECNT = 0. DSCNT can be set to 0 as there
is no need for the settling time for the touch panel and MUX.
To get a 200Hz output data rate, set DSCNT = 0, DMCNT = 0, and IDLECNT = 47.
15-6
NOTE:
Table 15-5. Output Data Rate Equations
Equations for Output Data Rate
(X,Y,X,Y, ...)
fclk
----------------------------------------------------------------------------------------------------------- -
× (
2 DSCNT DMCNT
+
(Z,X,Y,Z,X,Y, ....)
fclk
----------------------------------------------------------------------------------------------------------- -
× (
3 DSCNT DMCNT
+
(X,Y,U,X,Y,U, ...)
fclk
----------------------------------------------------------------------------------------------------------- -
× (
3 DSCNT DMCNT
+
(Z,X,Y,U,Z,X,Y,U, ...)
fclk
----------------------------------------------------------------------------------------------------------- -
× (
4 DSCNT DMCNT
+
fclk
-------------------------------------------------------------------------------------------------- -
(
DSCNT DMCNT
+ +
MC9328MX1 Reference Manual
( DSCNT 1 )
)
1 IDLECNT
+ +
( DSCNT 1 )
)
1 IDLECNT
+ +
( DSCNT 1 )
)
1 IDLECNT
+ +
( DSCNT 1 )
)
1 IDLECNT
+ +
(U,U,U, ...)
( DSCNT 0 )
)
1 IDLECNT
+
≥
≥
≥
≥
≥
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