DM6806 datasheet(33/64 Pages) ETC

33 / 64 page

4-3

Defining the I/O Map

The I/O map for the DM5806 is shown in Table 4-1 below. As shown, the board occupies 12 consecutive I/O

port locations. The base address (designated as BA) can be selected using DIP switch S1 as described in Chapter 1,

Board Settings. This switch can be accessed without removing the board from the connectorr. The following

sections describe the register contents of each address used in the I/O map.

BA + 0: PPI Port A — Digital I/O (Read/Write)

Transfers the 8-bit Port A digital input and digital output data between the board and an external device. A read

transfers data from the external device, through P2, and into PPI Port A; a write transfers the written data from

Port A through P2 to an external device.

BA + 1: PPI Port B — Digital I/O (Read/Write)

Transfers the 8-bit Port B digital input and digital output data between the board and an external device. A read

transfers data from the external device, through P2, and into PPI Port B; a write transfers the written data from

Port B through P2 to an external device.

BA + 2: PPI Port C — Digital I/O (Read/Write)

Transfers the two 4-bit Port C digital input and digital output data groups (Port C Upper and Port C Lower)

between the board and an external device. A read transfers data from the external device, through P2 and P6, and

into PPI Port C; a write transfers the written data from Port C through P2 and P6 to an external device.

Table 4-1: DM5806 I/O Map

Read Function

Write Function

Address *

(Decimal)

8255 PPI Port A

Read Port A digital input lines Program Port A digital output lines

BA + 0

8255 PPI Port B

Read Port B digital input lines Program Port B digital output lines

BA + 1

8255 PPI Port C

Read Port C digital input lines Program Port C digital output lines

BA + 2

8255 PPI Control Word

Not used

Program PPI configuration

BA + 3

IRQ Enable

Not used

Enable and disable interrupt

generation

BA + 4

Interrupt Status/Clear

Read status of interrupt

Clear interrupt

BA + 5

Reserved

BA + 6

Reserved

BA + 7

8254 Timer/Counter 0

Read TC0 count value

Load TC0 count register

BA + 8

8254 Timer/Counter 1

Read TC1 count value

Load TC1 count register

BA + 9

8254 Timer/Counter 2

Read TC2 count value

Load TC2 count register

BA + 10

8254 Control Word

Not used

Program control register

BA + 11

* BA = Base Address

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