ST10F269Z1Q6 datasheet(77/184 Pages) STMICROELECTRONICS

77 / 184 page

ST10F269

12 - PARALLEL PORTS

77/184

12.7.1 - Alternate Functions of Port 4

During external bus cycles that use segmentation

(address space above 64K Bytes) a number of

Port 4 pins may output the segment address lines.

The number of pins that is used for segment

address output determines the external address

space which is directly accessible. The other pins

of Port 4 may be used for general purpose I/O. If

segment address lines are selected, the alternate

function of Port 4 may be necessary to access

external memory directly after reset. For this

reason Port 4 will be switched to this alternate

function automatically.

The number of segment address lines is selected

via PORT0 during reset. The selected value can

be read from bitfield SALSEL in register RP0H

(read only) in order to check the configuration

during run time.

The CAN interfaces use 2 or 4 pins of Port 4 to

interface each CAN Modules to an external CAN

transceiver. In this case the number of possible

segment address lines is reduced.

The Table 21 summarizes the alternate functions

of Port 4 depending on the number of selected

segment

address

lines

(coded

via

bitfield

SALSEL)

Table 21 : Port 4 Alternate Functions

Port 4

Standard Function

SALSEL = 01

64K Bytes

Alternate Function

SALSEL = 11

256K Bytes

Alternate Function

SALSEL = 00

1M Byte

Alternate Function

SALSEL = 10

16M Bytes

P4.0

P4.1

P4.2

P4.3

P4.4

P4.5

P4.6

P4.7

GPIO

GPIO/CAN2_RxD

GPIO/CAN1_RxD

GPIO/CAN1_TxD

GPIO/CAN2_TxD

Segment Address A16

Segment Address A17

GPIO

GPIO/CAN2_RxD

GPIO/CAN1_RxD

GPIO/CAN1_TxD

GPIO/CAN2_TxD

Segment. Address A16

Segment Address A17

Segment Address A18

Segment Address A19

GPIO/CAN2_RxD

GPIO/CAN1_RxD

GPIO/CAN1_TxD

GPIO/CAN2_TxD

Segment Address A16

Segment Address A17

Segment Address A18

Segment Address A19

Segment Address A20

Segment Address A21

Segment Address A22

Segment Address A23

Figure 30 : Port 4 I/O and Alternate Functions

Port 4

Alternate Function

General Purpose

Input / Output

Segment Address

Lines

Cans I/O and General Purpose

Input / Output

P4.7

P4.6

P4.5

P4.4

P4.3

P4.2

P4.1

P4.0

A23

A22

A21

A20

A19

A18

A17

A16

CAN2_TxD

CAN1_TxD

CAN1_RxD

CAN2_RxD

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