PSD511B1 datasheet(90/153 Pages) STMICROELECTRONICS

90 / 153 page

PSD5XX Family

9.6.2.3 Configuring the Mode of Operation of the Counter/Timers:

Using the GLOBAL MODE bit of the Global Command register and MODE SELECT bit of

the Command register of Counter/Timers 0 – 3, individual Counter/Timer modes of operation

can be set up. Refer to Table 24. Notice that all the Counter/Timers can either operate in

Waveform/Pulse or Event Count/Time Capture modes, but not in all four modes at the same

time.

Counter/Timer

Registers

(Cont.)

Mode Select Bit

Global Mode Bit

(Command

Modes

(Global Command

Registers of

Counter/Timers

Counter/Timer2

0 – 3 CMD0, CMD1,

0, 1 and 3

CMD2 and CMD3)

Waveform

Waveform or

WatchDog

Pulse

Pulse or

WatchDog

Event Counter

WatchDog Only

Time Capture

WatchDog Only

9.6.2.4 Freeze Command Register

When a Microcontroller needs to access the contents of the Image Registers (IMG0-IMG3)

it does so by first setting the Command Register Freeze bit in order to disable the timer

state-machine accesses of the Image Register. The Microcontroller waits for the Freeze

Acknowledge bit in the Counter/Timer Status Register to be set to 1 and then it accesses

the Image Register as an address location. The freeze acknowledge signal effectively guar-

antees stable Image Register data during Microcontroller read/write cycles even though the

Counter/Timer continues to count. The Freeze Acknowledge bit gets cleared after the

negation of Freeze. The Freeze Command bits are set and cleared by the microcontroller

software.

The Freeze Command Register and the software Load/Store Register should not be set at

the same time. It is recommended that the registers be accessed individually.

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

***

Freeze

CTU3

CTU2

CTU1

CTU0

NOTE: * = Not used.

Table 24. Counter/Timer Modes

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