Datasheet

ST10F269 12 - PARALLEL PORTS
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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
GPIO
GPIO
GPIO/CAN2_RxD
GPIO/CAN1_RxD
GPIO/CAN1_TxD
GPIO/CAN2_TxD
Segment Address A16
Segment Address A17
GPIO
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
a)
General Purpose
Input / Output
b)
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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