SAB-C509-LM SIEMENS [Siemens Semiconductor Group], SAB-C509-LM Datasheet - Page 44

• Manufacturer Part Number: SAB-C509-LM
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

C509-L
Timer 2 Operation
Gated Timer Mode : In gated timer function, the external input pin P1.7/T2 operates as a gate to the
input of timer 2. lf T2 is high, the internal clock input is gated to the timer. T2 = 0 stops the counting
procedure.The external gate signal is sampled once every machine cycle.
Event Counter Mode : In the event counter function, the timer 2 is incremented in response to a 1-
to-0 transition at its corresponding external input pin P1.7/T2. In this function, the external input is
sampled every machine cycle. The maximum count rate is 1/12 of the oscillator frequency.
Reload of Timer 2 : Two reload modes are selectable:
In mode 0, when timer 2 rolls over from all 1’s to all 0’s, it not only sets TF2 but also causes the timer
2 registers to be loaded with the 16-bit value in the CRC register, which is preset by software.
In mode 1, a 16-bit reload from the CRC register is caused by a negative transition at the correspon-
ding input pin P1.5/T2EX.
Figure 19
Block Diagram of Timer 2
Semiconductor Group
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