参数资料
型号: IS80C52CXXX-12:D
厂商: TEMIC SEMICONDUCTORS
元件分类: 微控制器/微处理器
英文描述: 8-BIT, MROM, 12 MHz, MICROCONTROLLER, PQCC44
文件页数: 27/134页
文件大小: 3805K
122
8011Q–AVR–02/2013
ATmega164P/324P/644P
13.8
Compare Match Output Unit
The Compare Output mode (COMnx1:0) bits have two functions. The Waveform Generator uses
the COMnx1:0 bits for defining the Output Compare (OCnx) state at the next compare match.
Secondly the COMnx1:0 bits control the OCnx pin output source. Figure 13-5 shows a simplified
schematic of the logic affected by the COMnx1:0 bit setting. The I/O Registers, I/O bits, and I/O
pins in the figure are shown in bold. Only the parts of the general I/O Port Control Registers
(DDR and PORT) that are affected by the COMnx1:0 bits are shown. When referring to the
OCnx state, the reference is for the internal OCnx Register, not the OCnx pin. If a system reset
occur, the OCnx Register is reset to “0”.
Figure 13-5. Compare Match Output Unit, Schematic
The general I/O port function is overridden by the Output Compare (OCnx) from the Waveform
Generator if either of the COMnx1:0 bits are set. However, the OCnx pin direction (input or out-
put) is still controlled by the Data Direction Register (DDR) for the port pin. The Data Direction
Register bit for the OCnx pin (DDR_OCnx) must be set as output before the OCnx value is visi-
ble on the pin. The port override function is generally independent of the Waveform Generation
mode, but there are some exceptions. Refer to Table 13-2, Table 13-3 and Table 13-4 for
details.
The design of the Output Compare pin logic allows initialization of the OCnx state before the out-
put is enabled. Note that some COMnx1:0 bit settings are reserved for certain modes of
The COMnx1:0 bits have no effect on the Input Capture unit.
PORT
DDR
DQ
OCnx
Pin
OCnx
DQ
Waveform
Generator
COMnx1
COMnx0
0
1
D
ATA
B
U
S
FOCnx
clk
I/O
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