Motorola ColdFire MCF5281 - Manual (Page 367)

Programmable Interrupt Timers (PIT0–PIT3)
Freescale Semiconductor 19-7
When the PCSRn[OVW] bit is set, counter can be directly initialized by writing to PMRn without having
to wait for the count to reach 0x0000.
Figure 19-6. Counter in Free-Running Mode
19.3.3 Timeout Specifications
The 16-bit PIT counter and prescaler supports different timeout periods. The prescaler divides the internal
bus clock period as selected by the PCSRn[PRE] bits. The PMRn[PM] bits select the timeout period.
Eqn. 19-1
19.3.4 Interrupt Operation
Table 19-6 shows the interrupt request generated by the PIT.
The PIF flag is set when the PIT counter reaches 0x0000. The PIE bit enables the PIF flag to generate
interrupt requests. Clear PIF by writing a 1 to it or by writing to the PMR.
Table 19-6. PIT Interrupt Requests
Interrupt Request Flag Enable Bit
Timeout PIF PIE
0x0002 0x0001 0x0000 0xFFFF
0x0005
PIT CLOCK
COUNTER
MODULUS
PIF
Timeout period
2 PCSRn[PRE] (PMRn[PM] 1) +
×
f
sys
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MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3