isppac10 Lattice Semiconductor Corp., isppac10 Datasheet - Page 6

• Manufacturer Part Number: isppac10
• Description: In-system Programmable Analog Circuit
• Manufacturer: Lattice Semiconductor Corp.

Lattice Semiconductor
Product Term Sharing Array
The Product Term Sharing Array (PTSA) consists of 32 inputs from the Dual-OR Array (Expandable PTSA OR) and
32 outputs directly to the macrocells. Each output is the OR term of any combination of the seven Expandable
PTSA OR terms connected to that output. Every Nth macrocell is connected to N-3, N-2, N-1, N, N+1, N+2 and
N+3 PTSA OR terms via a programmable connection. This wraps around the logic, Macrocell 0 gets its logic from
29, 30, 31, 0, 1, 2, 3. The Expandable PTSA OR used in conjunction with the PTSA allows wide functions to be
implemented easily and efficiently. Without using the Expandable PTSA OR capability, the greatest number of
product terms that can be included in a single function with one pass of delay is 35. Figure 6 shows the graphical
representation of the PTSA.
Figure 6. Product Term Sharing Array
Macrocell
The 32 registered macrocells in the GLB are driven by the 32 outputs from the PTSA or the PTSA bypass. Each
macrocell contains a programmable XOR gate, a programmable register/latch flip-flop and the necessary clocks
and control logic to allow combinatorial or registered operation.
The macrocells each have two outputs, which can be fed to the SRP, GRP and I/O cell. This dual or concurrent out-
put capability from the macrocell gives efficient use of the hardware resources. One output can be a registered
function for example, while the other output can be an unrelated combinatorial function. A direct register input from
the I/O cell facilitates efficient use of the macrocell to construct high-speed input registers.
Macrocell registers can be clocked from one of several global or product term clocks available on the device. A glo-
bal and product term clock enable is also provided, eliminating the need to gate the clock to the macrocell registers
directly. Reset and preset for the macrocell register is provided from both global and product term signals. The
macrocell register can be programmed to operate as a D-type register or a D-type latch. Figure 7 is a graphical rep-
resentation of the ispMACH 5000VG macrocell.
PTSA OR 29
PTSA OR 30
PTSA OR 31
PTSA OR 0
PTSA OR 1
PTSA OR 2
PTSA OR 3
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ispMACH 5000VG Family Data Sheet
Macrocell 0
Macrocell 1
Macrocell 2
Macrocell 29
Macrocell 30
Macrocell 31