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uPSD3212A, uPSD3212C, uPSD3212CV
Product Term Allocator
The CPLD has a Product Term Allocator. PSDsoft
uses the Product Term Allocator to borrow and
place product terms from one macrocell to anoth-
er. The following list summarizes how product
terms are allocated:
–
McellAB0-McellAB7 all have three native
product terms and may borrow up to six more
–
McellBC0-McellBC3 all have four native
product terms and may borrow up to five more
–
McellBC4-McellBC7 all have four native
product terms and may borrow up to six more.
Each macrocell may only borrow product terms
from certain other macrocells. Product terms al-
ready in use by one macrocell are not available for
another macrocell.
If an equation requires more product terms than
are available to it, then “external” product terms
are required, which consume other Output Macro-
cells (OMC). If external product terms are used,
extra delay is added for the equation that required
the extra product terms.
This is called product term expansion. PSDsoft
Express performs this expansion as needed.
Loading and Reading the Output Macrocells
(OMC). The Output Macrocells (OMC) block oc-
cupies a memory location in the MCU address
space, as defined by the CSIOP block (see
). The flip-
flops in each of the 16 Output Macrocells (OMC)
can be loaded from the data bus by a MCU. Load-
ing the Output Macrocells (OMC) with data from
the MCU takes priority over internal functions. As
such, the preset, clear, and clock inputs to the flip-
flop can be overridden by the MCU. The ability to
load the flip-flops and read them back is useful in
such applications as loadable counters and shift
registers, mailboxes, and handshaking protocols.
Data can be loaded to the Output Macrocells
(OMC) on the trailing edge of WRITE Strobe (WR,
edge loading) or during the time that WRITE
Strobe (WR) is active (level loading). The method
of loading is specified in PSDsoft Express Config-
uration.
Figure 57. CPLD Output Macrocell
PT
ALLOCATOR
MASK
REG.
PT CLK
PT
PT
PT
CLKIN
FEEDBACK (.FB)
PORT INPUT
AND ARRAY
PLD INPUT BUS
MUX
MUX
POLARITY
SELECT
LD
IN
CLR
Q
PR
DIN
COMB/REG
SELECT
PORT
DRIVER
INPUT
MACROCELL
I/O PIN
MACROCELL
ALLOCATOR
MCU DATA BUS
D [ 7:0]
DIRECTION
REGISTER
CLEAR (.RE)
PROGRAMMABLE
FF (D / T/JK /SR)
WR
ENABLE (.OE)
PRESET(.PR)
RD
MACROCELL CS
AI06617
www.BDTIC.com/ST
