Quatech RS-422/485, MPA-200/300 user manual Addressing, Base Address = 3F8H

5 ADDRESSING

The MPA-200 occupies a continuous 8 byte block of I/O addresses. For example, if the base address is set to 300H, then the MPA-200 will occupy address locations 300H-307H. The base address of the MPA-200 may be set to any of the first 64 Kbytes (0 - FFFFH) of available I/O address space through the settings of dip switches SW1 and SW2. SW1 allows the user to select the higher address signals A15 - A8. SW2 allows the user to select the lower address signals A7 - A3. The sixth position of SW2 is not used and can be ignored. Figure 2 shows some examples of different base addresses.

Figure 1 Address switch selection examples.

	A15	A14	A13	A12	A11	A10	A9	A8
	ON
SW1	1	2	3	4	5	6	7	8

	A7
	ON
SW2	1

A6 A5 A4 A3 NOT USED

2 3 4 5 6

Base Address = 300H

A15 A14 A13 A12 A11 A10 A9 A8

ON

A7 A6 A4 A5 A3 NOT USED

O N

SW1

1 2 3 4 5 6 7 8 SW2 1 2 3 4 5 6

Base Address = 3F8H

15 Quatech Inc., MPA-200/300 Manual