General-purpose timers (TIM21/22) RM0367
596/1043 RM0367 Rev 7
Note: The states of the external I/O pins connected to the standard OCx channels depend on the
state of the OCx channel and on the GPIO registers.
22.4.9 TIM21/22 counter (TIMx_CNT)
Address offset: 0x24
Reset value: 0x0000
22.4.10 TIM21/22 prescaler (TIMx_PSC)
Address offset: 0x28
Reset value: 0x0000
22.4.11 TIM21/22 auto-reload register (TIMx_ARR)
Address offset: 0x2C
Reset value: 0xFFFF
Table 104. Output control bit for standard OCx channels
CCxE bit OCx output state
0 Output disabled (OCx=’0’, OCx_EN=’0’)
1 OCx=OCxREF + Polarity, OCx_EN=’1’
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CNT[15:0]
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Bits 15:0 CNT[15:0]: Counter value
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PSC[15:0]
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Bits 15:0 PSC[15:0]: Prescaler value
The counter clock frequency (CK_CNT) is equal to f
CK_PSC
/ (PSC[15:0] + 1).
PSC contains the value to be loaded in the active prescaler register at each update event
(including when the counter is cleared through UG bit of TIMx_EGR register or through
trigger controller when configured in “reset mode”).
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ARR[15:0]
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Bits 15:0 ARR[15:0]: Auto-reload value
ARR is the value to be loaded into the actual auto-reload register.
Refer to the Section 22.3.1: Timebase unit on page 549 for more details about ARR update
and behavior.
The counter is blocked while the auto-reload value is null.