PIC18F44J50-I Datasheet, PDF (183/562 Pages) Microchip Technology – 28/44-Pin, Low-Power, High-Performance USB Microcontrollers

PIC18F46J50 FAMILY
11.3 MASTER PORT MODES
In its Master modes, the PMP module provides an 8-bit
data bus, up to 16 bits of address, and all the necessary
control signals to operate a variety of external parallel
devices, such as memory devices, peripherals and
slave microcontrollers. To use the PMP as a master,
the module must be enabled (PMPEN = 1) and the
mode must be set to one of the two possible Master
modes (PMMODEH<1:0> = 10 or 11).
Because there are a number of parallel devices with a
variety of control methods, the PMP module is designed
to be extremely flexible to accommodate a range of
configurations. Some of these features include:
• 8-Bit and 16-Bit Data modes on an 8-bit data bus
• Configurable address/data multiplexing
• Up to two chip select lines
• Up to 16 selectable address lines
• Address auto-increment and auto-decrement
• Selectable polarity on all control lines
• Configurable Wait states at different stages of the
read/write cycle
11.3.1 PMP AND I/O PIN CONTROL
Multiple control bits are used to configure the presence
or absence of control and address signals in the
module. These bits are PTBEEN, PTWREN, PTRDEN
and PTEN<15:0>. They give the user the ability to con-
serve pins for other functions and allow flexibility to
control the external address. When any one of these
bits is set, the associated function is present on its
associated pin; when clear, the associated pin reverts
to its defined I/O port function.
Setting a PTENx bit will enable the associated pin as
an address pin and drive the corresponding data
contained in the PMADDR register. Clearing a PTENx
bit will force the pin to revert to its original I/O function.
For the pin configured as chip select (PMCS) with the
corresponding PTENx bit set, the PTEN0 and PTEN1
bits will also control the PMALL and PMALH signals.
When multiplexing is used, the associated address
latch signals should be enabled.
11.3.2 READ/WRITE CONTROL
The PMP module supports two distinct read/write
signaling methods. In Master Mode 1, read and write
strobes are combined into a single control line,
PMRD/PMWR. A second control line, PMENB, deter-
mines when a read or write action is to be taken. In
Master Mode 2, separate read and write strobes
(PMRD and PMWR) are supplied on separate pins.
All control signals (PMRD, PMWR, PMBE, PMENB,
PMAL and PMCS) can be individually configured as
either positive or negative polarity. Configuration is
controlled by separate bits in the PMCONL register.
Note that the polarity of control signals that share the
same output pin (for example, PMWR and PMENB) are
controlled by the same bit; the configuration depends
on which Master Port mode is being used.
11.3.3 DATA WIDTH
The PMP supports data widths of both 8 bits and
16 bits. The data width is selected by the MODE16 bit
(PMMODEH<2>). Because the data path into and out
of the module is only 8 bits wide, 16-bit operations are
always handled in a multiplexed fashion, with the Least
Significant Byte (LSB) of data being presented first. To
differentiate data bytes, the byte enable control strobe,
PMBE, is used to signal when the Most Significant Byte
(MSB) of data is being presented on the data lines.
11.3.4 ADDRESS MULTIPLEXING
In either of the Master modes (PMMODEH<1:0> = 1x),
the user can configure the address bus to be multiplexed
together with the data bus. This is accomplished by
using the ADRMUX<1:0> bits (PMCONH<4:3>). There
are three Address Multiplexing modes available. Typical
pinout configurations for these modes are displayed in
Figure 11-9, Figure 11-10 and Figure 11-11.
In Demultiplexed mode (PMCONH<4:3> = 00), data and
address information are completely separated. Data bits
are presented on PMD<7:0>, and address bits are
presented on PMADDRH<6:0> and PMADDRL<7:0>.
In Partially Multiplexed mode (PMCONH<4:3> = 01), the
lower eight bits of the address are multiplexed with the
data pins on PMD<7:0>. The upper eight bits of address
are unaffected and are presented on PMADDRH<6:0>.
The PMA0 pin is used as an address latch and presents
the Address Latch Low (PMALL) enable strobe. The
read and write sequences are extended by a complete
CPU cycle, during which, the address is presented on
the PMD<7:0> pins.
In Fully Multiplexed mode (PMCONH<4:3> = 10), the
entire 16 bits of the address are multiplexed with the
data pins on PMD<7:0>. The PMA0 and PMA1 pins are
used to present Address Latch Low (PMALL) enable
strobes and Address Latch High (PMALH) enable
strobes, respectively. The read and write sequences
are extended by two complete CPU cycles. During the
first cycle, the lower eight bits of the address are
presented on the PMD<7:0> pins with the PMALL
strobe active. During the second cycle, the upper eight
bits of the address are presented on the PMD<7:0>
pins with the PMALH strobe active. In the event the
upper address bits are configured as chip select pins,
the corresponding address bits are automatically
forced to ‘0’.
 2011 Microchip Technology Inc.
DS39931D-page 183