ST10F280_12 datasheet(108/239 Pages) STMICROELECTRONICS

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Parallel ports

ST10F280

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Doc ID 8673 Rev. 3

The port output latch is clocked by the signal “Compare Trigger” which is generated by the

CAPCOM unit. In compare mode 3, when a match occurs, the value '1' is written to the port

output latch via the line “Alternate Data Output”. When an overflow of the corresponding

timer occurs, a '0' is written to the port output latch. In both cases, 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 below, 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 (200 ns sample rate at 40MHz CPU clock).

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).

P2.15 in addition serves as input for CAPCOM2 timer T7 (T7IN).

The table below summarizes the alternate functions of Port 2.

Table 18.

Port 2 alternate function

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 Timer T7 Ext. Count Input

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