C167CS datasheet(152/517 Pages) INFINEON

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C167CS

Derivatives

Parallel Ports

User’s Manual

7-25

V2.0, 2000-07

Alternate Functions of Port 2

All Port 2 lines (P2.15 … P2.0) serve as capture inputs or compare outputs

(CC15IO … CC0IO)

for

the

CAPCOM1

unit.

The

upper

eight

Port 2

lines

(P2.15 … P2.8) also serve as external interrupt inputs EX7IN … EX0IN (16 TCL sample

rate).

When a Port 2 line is used as a capture input, the state of the input latch, which

represents the state of the port pin, is directed to the CAPCOM unit via the line “Alternate

Pin Data Input”. If an external capture trigger signal is used, the direction of the

respective pin must be set to input. If the direction is set to output, the state of the port

output latch will be read since the pin represents the state of the output latch. This can

be used to trigger a capture event through software by setting or clearing the port latch.

Note that in the output configuration, no external device may drive the pin, otherwise

conflicts would occur.

When a Port 2 line is used as a compare output (compare modes 1 and 3), the compare

event (or the timer overflow in compare mode 3) directly effects the port output latch. In

compare mode 1, when a valid compare match occurs, the state of the port output latch

is read by the CAPCOM control hardware via the line “Alternate Latch Data Input”,

inverted, and written back to the latch via the line “Alternate Data Output”. 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 (sample rate 16 TCL) or as Fast External Interrupt

inputs (sample rate 2 TCL).

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

Table 7-4 summarizes the alternate functions of Port 2.

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