ST10F269ZX datasheet(69/184 Pages) STMICROELECTRONICS

69 / 184 page

ST10F269

12 - PARALLEL PORTS

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the output latch is clocked by the signal “Compare

Trigger”.

The direction of the pin should be set to output by

the user, otherwise the pin will be in the

high-impedance state and will not reflect the state

of the output latch.

As can be seen from the port structure in

Figure 26, the user software always has free

access to the port pin even when it is used as a

compare output. This is useful for setting up the

initial level of the pin when using compare mode 1

or the double-register mode. In these modes,

unlike in compare mode 3, the pin is not set to a

specific value when a compare match occurs, but

is toggled instead.

When the user wants to write to the port pin at the

same time a compare trigger tries to clock the

output latch, the write operation of the user

software has priority. Each time a CPU write

access to the port output latch occurs, the input

multiplexer of the port output latch is switched to

the line connected to the internal bus. The port

output latch will receive the value from the internal

bus and the hardware triggered change will be

lost.

As all other capture inputs, the capture input

function of pins P2.15...P2.0 can also be used as

external interrupt inputs (200ns sample rate at

40MHz CPU clock on PQFP144 devices and

250ns sample rate at 32MHz CPU clock on

TQFP144 devices).

The upper eight Port 2 lines (P2.15...P2.8) also

can serve as Fast External Interrupt inputs from

EX0IN to EX7IN (Fast external interrupt sampling

rate is 25ns at 40MHz CPU clock and 31.25ns at

32MHz CPU clock).

P2.15 in addition serves as input for CAPCOM2

timer T7 (T7IN). The Table 19 summarizes the

alternate functions of Port 2.

Table 19 : Alternate Functions of Port 2

Port 2 Pin

Alternate Function a)

Alternate Function b)

Alternate Function c)

P2.0

P2.1

P2.2

P2.3

P2.4

P2.5

P2.6

P2.7

P2.8

P2.9

P2.10

P2.11

P2.12

P2.13

P2.14

P2.15

CC0IO

CC1IO

CC2IO

CC3IO

CC4IO

CC5IO

CC6IO

CC7IO

CC8IO

CC9IO

CC10IO

CC11IO

CC12IO

CC13IO

CC14IO

CC15IO

EX0IN

Fast External Interrupt 0 Input

EX1IN

Fast External Interrupt 1 Input

EX2IN

Fast External Interrupt 2 Input

EX3IN

Fast External Interrupt 3 Input

EX4IN

Fast External Interrupt 4 Input

EX5IN

Fast External Interrupt 5 Input

EX6IN

Fast External Interrupt 6 Input

EX7IN

Fast External Interrupt 7 Input

T7IN T7 External Count Input

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