PIC32MX440F256H-80I Datasheet, PDF (456/646 Pages) Microchip Technology – 64/100-Pin General Purpose and USB 32-Bit Flash Microcontrollers

PIC32MX3XX/4XX
FIGURE 20-6:
FULL MULTIPLEXED
ADDRESSING
(16-BIT BUS)
PIC32MX3XX/4XX
ADRMUX<1:0> = 11
PMD<7:0>
PMD<15:8> ₍₁₎
PMA14/PMCS1
PMA15/PMCS2
PMA0 / PMALL
PMA1 / PMALH
PMRD
PMWR
Fully Multiplexed Address/Data Bus
Control Lines
Note 1: PMA15 is not available if PMCS2 is enabled.
PMA14 is not available if PMCS1 is enabled.
20.2.16 ADDRESSING CONSIDERATIONS
PMCS2 and PMCS1 Chip Select pins share functional-
ity with address lines A15 and A14. It is possible to
enable both PMCS2 and PMCS1 as Chip Selects, or
enable only PMCS2 as a Chip Select, allowing PMCS1
to function strictly as address line A14. It is not possible
to enable only PMCS1.
When configured as Chip Selects, a 1 must be written
into bit position 15 or 14 of the PMADDR register in
order for PMCS2 or PMCS1 to become active during a
read or write operation. Failing to write a 1 to PMCS2
or PMCS1 does not prevent address pins PMA<13:0>
from being active as the specified address appears,
however, no Chip Select signal will be active.
Note:
When using Auto-Increment Address
mode, PMCS2 and PMCS1 do not partic-
ipate and must be controlled by the user’s
software by writing to ‘1’ to
PMADDR<15:14> explicitly.
Disabling one or both Chip Selects PMCS2 and
PMCS1 makes these pins available as address lines
A15 and A14.
In Full Multiplexed mode, address bits
PMADDR<15:0> are multiplexed with the data bus and
in the event address bits PMA15 or PMA14 are config-
ured as Chip Selects, the corresponding
PMADDR<15:14> address bits are automatically
forced = 0. Disabling one or both PMCS2 and PMCS1
makes these bits available as address bits
PMADDR<15:14>.
In any of the Master mode multiplexing schemes, dis-
abling both Chip Select pins PMCS2 and PMCS1
requires the user to provide Chip Select line control
through some other I/O pin under software control. See
Figure 20-7.
FIGURE 20-7:
PMP CHIP SELECT ADDRESS MAPPING (DEMULTIPLEXED AND PARTIAL
MULTIPLEXED MODES)
0xFFFF
PMCS2, CS1
Both Devices
Selected
11
0xC000 ^(INVALID)
0x8000
0x4000
Device 2
Selected
PMCS2 = 1
Device 1
Selected
PMCS1 = 1
10
01
No Device
Selected
00
0x0000
2 - Chip Selects
2 - 16K Address Ranges
PMCS2, A14
Device
Selected
PMCS2 = 1
11
10
No Device
Selected
01
00
1 - Chip Select
1 - 32K Address Range
A15, A14, IO-pin
Device
Selected
IOpin = 1
111
10 1
011
0 01
IO-pin = Software controlled CS
1 - 64K Address Range
DS61143E-page 454
Preliminary
© 2008 Microchip Technology Inc.