XC2000 datasheet(71/729 Pages) INFINEON

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XC2000 Derivatives

Peripheral Units (Vol. 2 of 2)

The General Purpose Timer Units

Preliminary

User’s Manual

14-53

V1.0, 2007-06

GPT_X7, V2.0

14.2.6

GPT2 Clock Signal Control

All actions within the timer block GPT2 are triggered by transitions of its basic clock. This

basic clock is derived from the system clock by a basic block prescaler, controlled by

bitfield BPS2 in register T6CON (see Figure 14-20). The count clock can be generated

in two different ways:

• Internal count clock, derived from GPT2’s basic clock via a programmable prescaler,

is used for (gated) timer mode.

• External count clock, derived from the timer’s input pin(s), is used for counter mode.

For both ways, the basic clock determines the maximum count frequency and the timer’s

resolution:

Internal Count Clock Generation

In timer mode and gated timer mode, the count clock for each GPT2 timer is derived from

the GPT2 basic clock by a programmable prescaler, controlled by bitfield TxI in the

respective timer’s control register TxCON.

The count frequency

Tx for a timer Tx and its resolution rTx are scaled linearly with lower

clock frequencies, as can be seen from the following formula:

[14.2]

The effective count frequency depends on the common module clock prescaler factor

F(BPS2) as well as on the individual input prescaler factor 2

<TxI>. Table 14-15

summarizes the resulting overall divider factors for a GPT2 timer that result from these

cascaded prescalers.

Table 14-14 Basic Clock Selection for Block GPT2

Block Prescaler

1) Please note the non-linear encoding of bitfield BPS2.

BPS2 = 01

BPS2 = 00

2) Default after reset.

BPS2 = 11

BPS2 = 10

Prescaling Factor

for GPT2: F(BPS2)

F(BPS2)

= 2

F(BPS2)

= 4

F(BPS2)

= 8

F(BPS2)

= 16

Maximum External

Count Frequency

GPT/4

GPT/8

GPT/16

GPT/32

Input Signal

Stable Time

× t

GPT

× t

GPT

× t

GPT

× t

GPT

fTx

fGPT

FBPS2

() 2

<Txl>

---------------------------------------------

rTx µs

[]

FBPS2

() 2

<Txl>

fGPT MHz

[]

---------------------------------------------

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