Texas Instruments MSC1210 2. Timer Modes and Usage, TxM1 TxM0 Timer Description of Timer Mode

Models: MSC1210

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Using Timers to Measure Time

As is shown in the previous chart, four bits (two for each timer) are used to specify a mode of operation. The modes of operation are shown in Table 8−2.

Table 8−2. Timer Modes and Usage

TxM1

TxM0

Timer

Description of Timer Mode

Timer 1

Timer 0

 

 

Mode

 

 

 

 

 

 

 

 

 

0

0

0

13-bit timer/counter

Y

Y

 

 

 

 

 

 

0

1

1

16-bit timer/counter

Y

Y

 

 

 

 

 

 

1

0

2

8-bit timer/counter with auto-reload

Y

Y

 

 

 

 

 

 

1

1

3

Two 8-bit counters (split timer mode)

N

Y

 

 

 

 

 

 

The TMOD.GATE bit controls gating of the timer/counter. If TMOD.GATE is cleared, the timer/counter increments only if TCON.TRx is set. If TMOD.GATE is set, the timer/counter increments only if TCON.TRx is set and the corre- sponding INTx pin is held high. This feature can be used for pulse width mea- surements.

The TMOD.CT bit selects counter or timer operation. If TMOD.CT is cleared, the timer/counter register is incremented on either fosc/4 or fosc/12 (based on

the state of CKCON.TxM ). If TMOD.CT is set, the timer/counter register is in- cremented by the Tx pin.

8.3.3.113-Bit Time Mode (mode 0)

Timer mode 0 is a 13-bit timer. This is a relic that was kept around in the 8052 (and subsequently MSC1210) to maintain compatibility with its predecessor, the 8048. The 13-bit timer mode is not normally used in new development.

In this mode, the timer/counter uses five bits of the TLx register and all eight bits of the THx register for the 13-bit register. Therefore, the upper three bits of TLx must be masked if they are used by software. When the timer/counter rolls over on a transition from 01FFFH, the timer/counter interrupt flag is set (TCON.TFx).

Figure 8−1. Timer 0/1 Block Diagram for Modes 0 and 1

8-6

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Texas Instruments MSC1210 manual 2. Timer Modes and Usage, TxM1 TxM0 Timer Description of Timer Mode