PSD501B1 datasheet(87/153 Pages) STMICROELECTRONICS

87 / 153 page

PSD5XX Family

9.6.2.2 Command Registers for Counter/Timers CMD0, CMD1, CMD2, CMD3:

Each of the Counter/Timer units (CTU) has one Command Register associated with it.

A description of these various CTU command bits is provided below. Refer to CSIOP

Tables 23 and 24 for their addresses and selection details. Figure 43 describes the

Command Register bits.

The following is the description of Counter/Timer0 CMD0 register bits. Bits in CMD1, CMD2

and CMD3 have similar descriptions. Refer to Figure 43 also.

Counter/Timer

Registers

(Cont.)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Enable/

Software

Pin /

Input

Output

Select

Increment /

Mode

Disable

Gating

PPLD

Polarity

Counter

Decrement

Select

Using

Bit for

Macrocell

Pin,

Load /

PPLD

Store cmd

Macrocell

Using Pin

or PPLD

Software

Macrocell

NOTES: 1. At RESET these bits come up as 0s.

2. In WatchDog Mode, CMD2 register bits are Don’t Cares.

Mode Select Bit (0):

This bit selects the Counter/Timer0 operation mode. After

RESET Counter/Timer0 initializes in waveform/event count

mode. When this bit is set to

1: The Counter/Timer0 operates in Pulse/Time capture

modes.

0: The Counter/Timer0 operates in Waveform/Event count

modes.

NOTE: See Table 24 for details of Timer mode set up.

Increment/Decrement Bit (1): This bit is used to set the Counter/Timer in increment or

decrement mode. The RESET state is Decrement mode.

When this bit is set to

1: The Counter/Timer0 is in increment mode.

0: The Counter/Timer0 is in decrement mode.

NOTE: In WatchDog mode Counter #2 is in decrement

mode only.

Select Counter Bit (2):

This bit is used to select or deselect Counter/Timer0.

At RESET this bit initializes as 0 which means

Counter/Timer0 is deselected. When this bit is set to

1: Counter/Timer0 is selected (counting enabled).

0: Counter/Timer0 is deselected (counting disabled).

After a Counter/Timer is started by the Global Command Register, it can be re-configured by

changing the individual Command Register. The steps to re-configure a Counter/Timer are:

1. Disable the Counter/Timer by writing a “0” to the Select Counter Bit (bit 2) of the

Command Register.

2. Change the Counter/Timer configuration by writing the new value (bit 2 remains at “0”)

to the Command Register.

3. Enable the Counter/Timer again by writing the new value with bit 2 set to “1” to the

Command Register.

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