Sundance Spas ST201 - Manual (Page 63)

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Sundance Technology ST201 PRELIMINARY draft 2
COUNTDOWN
Class....................I/O Registers, Interrupt
Base Address ......IoBaseAddress register value
Address Offset .....0x48
Access Mode .......Read/Write
Width ...................16 bits
Countdown is a programmable down-counter that will generate an interrupt upon its expiration. If the
CountdownIntEnable bit in DMACtrl is set, the IntRequested interrupt will be generated when Countdown
counts through zero. Countdown has two modes of operation that is selected by the CountdownMode bit in
DMACtrl.When CountdownMode is cleared, Countdown is loaded by the host software with an initial
countdown value, then decrements at a rate determined by the CountdownSpeed bit in DMACtrl. When
CountdownSpeed is cleared, the count rate is once every 3.2 us. When CountdownSpeed is set, the count
rate is once every 320 ns. When Countdown reaches zero, it continues to count down, wrapping to 0xffff.
When CountdownMode is set, Countdown begins counting only when TxDMAComplete in IntStatus
becomes set. Countdown is cleared by reset.
BIT BIT NAME BIT DESCRIPTION
15..0 Countdown Value of current state of Countdown timer.