TS68230CP8 datasheet(41/61 Pages) STMICROELECTRONICS

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counter preload register or continues counting when zero detect is reached ; bit 3 is unused and is read as zero

; bits 2 and 1 configure the path from the CLK and TIN pins to the counter controller ; and bit 0 ena-bles the timer.

This register is readable and writable at all times. All bits are cleared to zero when the RESET pin is asserted.

TCR

7 6 5

TOUT/TIACK Control

0 0 X

The dual-function pins PC3/TOUT and PC7/TIACK carry the port C function.

0 1 X

The dual-function pin PC3/TOUT carries the TOUT function. In the run state it is used as a square-

wave output and is toggled on zero detect. The TOUT pin is high while in the halt state. The dual-

function pin PC7/TIACK carries the PC7 function.

1 0 0

The dual-function pin PC3/TOUT carries the TOUT function. In the run or halt state it is used as

a timer interrupt request output. The timer interrupt is disabled, thus, the pin is always three stated.

The dual-function pin PC7/TIACK carries the TIACK function ; however, since interrupt request is

negated, the PI/T produces no response (i.e., no data or DTACK) to an asserted TIACK. Refer to

5.1.3. Timer Interrupt Acknowledge Cycles for details.

1 0 1

The dual-function pin PC3/TOUT carries the TOUT function and is used as a timer interrupt request

output. The timer interrupt is enabled ; thus, the pin is low when the timer ZDS status bit is one.

The dual-function pin PC7/TIACK carries the TIACK function and is used as a timer interrupt ac-

knowledge input. Refer to the 5.1.3. Timer Interrupt Acknowledge Cycles for details. This combi-

nation supports vectored timer interrupts.

1 1 0

The dual-function pin PC3/TOUT function. In the run or halt state it is used as a timer interrupt

request output. The timer interrupt is disabled ; thus, the pin is always three-stated. The dual-func-

tion pin PC7/TIACK carries the PC7 function.

1 1 1

The dual-function pin PC3/TOUT carries the TOUT function and is used as a timer interrupt request

output. The timer interrupt is enabled ; thus, the pin is low when the timer ZDS status bit is one.

The dual-function pin PC7/TIACK carries the PC7 function and autovectored interrupts are sup-

ported.

TCR

Zero Detect Control

The counter is loaded from the counter preload register on the first clock to the 24-bit counter after

zero detect, then resumes counting.

The counter rolls over on zero detect, then continues counting.

TCR

Unused and is always read as zero.

TCR

2 1

Clock Control

0 0

The PC2/TIN input pin carries the port C function, and the CLK pin and prescaler are used. The

prescaler is decremented on the falling transition of the CLK pin ; the 24-bit counter is decremented,

rolls over, or is loaded from the counter preload registers when the prescaler rolls over from $OO

to $1F. The timer enable bit determines whether the timer is in the run or halt state.

0 1

The PC2/TIN pin serves as a timer input, and the CLK pin and prescaler are used. The prescaler

is decremented on the falling transition of the CLK pin ; the 24-bit counter is decremented, rolls

over, or is loaded from the counter preload registers when the prescaler rolls over from $00 to $1F.

The timer is in the run state when the timer enable bit is one and the TIN pin is high ; otherwise,

the timer is in the halt state.

1 0

The PC2/TIN pin serves as a timer input and the prescaler is used. The prescaler is decremented

TS68230

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