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XC161 Derivatives
Peripheral Units (Vol. 2 of 2)
Capture/Compare Units
User’s Manual
17-22
V2.2, 2004-01
CC12_X1, V2.1
Case 5 shows an option to get around this problem. Here, the compare register is
reloaded with FFF8
H
, a value which is lower than the timer reload value. Thus, the timer
will never reach this value, and no compare match will be detected. The output signal will
be set to 0 after the first timer overflow. However, after the second overflow, software
now reloads the compare register with a regular compare value. As no compare blocking
has taken place (since there was no compare match), the newly written compare value
will go into effect during the current timer period.
17.5.5
Double-Register Compare Mode
The Double-Register Compare Mode makes it possible to further reduce software
overhead for a number of applications. In this mode, two compare registers work
together to control one output. This mode is selected via the DRM register, or by a
special combination of compare modes for the two registers.
For double-register compare mode, the 16 capture/compare registers of a CAPCOM unit
are regarded as two banks of 8 registers each. The lower eight registers form bank1,
while the upper eight registers form bank2. For double-register mode, a bank1 register
and a bank2 register form a register pair. Both registers of this register pair operate on
the pin associated with the bank1 register.
The relationship between the bank1 and bank2 register of a pair and the effected output
pins for double-register compare mode is listed in
The double-register compare mode can be programmed individually for each register
pair. Double-register compare mode can be selected via a certain combination of
compare modes for the two registers of a pair. The bank1 register must be programmed
Table 17-3
Register Pairs for Double-Register Compare Mode
CAPCOM1 Unit
CAPCOM2 Unit
Register Pair
Used
Output
Pin
Control
Bitfield in
CC1DRM
Register Pair
Used
Output
Pin
Control
Bitfield in
CC2DRM
Bank 1
Bank 2
Bank 1
Bank 2
CC0
CC8
CC0IO
DR0M
CC16
CC24
CC16IO
DR0M
CC1
CC9
CC1IO
DR1M
CC17
CC25
CC17IO
DR1M
CC2
CC10
CC2IO
DR2M
CC18
CC26
CC18IO
DR2M
CC3
CC11
CC3IO
DR3M
CC19
CC27
CC19IO
DR3M
CC4
CC12
CC4IO
DR4M
CC20
CC28
CC20IO
DR4M
CC5
CC13
CC5IO
DR5M
CC21
CC29
CC21IO
DR5M
CC6
CC14
CC6IO
DR6M
CC22
CC30
CC22IO
DR6M
CC7
CC15
CC7IO
DR7M
CC23
CC31
CC23IO
DR7M