1. It is partitioned into 4 quadrants, each containing 12 macrocells.
EP1800
EP1800 is the most complex device among the general purpose EPLDs offered by Altera Corp.
It has 12 dedicated inputs, 4 clock inputs, and 48 I/O pins each of which can be configured as an input or an output.
It is partitioned into 4 quadrants, each containing 12 macrocells.
The macrocells within each quadrant are categorized into 2 types:
Local macrocells
Global macrocells
Out of 12 macrocells in a quadrant, 8 are local and 4 are global.

2. A separate clock line is provided for each group of macrocells.
Each quadrant of macrocells has its own local bus.
These bus lines carries the true and complemented outputs of the macrocells within the quadrant. Thus having 24 lines in the local bus.
A global bus is runs through all 4 quadrants and has 64 lines.
These bus lines carries the true and complement signals of the 12 dedicated inputs, 4 clock inputs, and the I/O pins of 4 global macrocells in each quadrant.

3. EP1800

4. EP1800
The combinational or registered output of local macrocell, or the signal on its I/O pin are fed back to the local bus of the quadrant to which the macrocell belongs.

5. EP1800
The combinational or registered output of global macrocell are fed back to the local bus of the quadrant, and the signal on its I/O pin is fed back to the global bus.
Thus the local macrocells provide feedback within quardants and global macrocells provide feedback between quadrants.

6. EP1800
As in EP600, EP1800 is also consists programmable flip-flop in a macrocell (i.e., it can be configured for D, T, JK, or SR operation).
In synchronous clocking the flip-flop can be clocked by the quadrant clock of the macrocell, and the output buffer is controlled by the dedicated product term.

7. EP1800
In asynchronous cocking the flip-flop is clocked via the product term, and the output buffer is permanently enabled.
One additional mode of operation allowed for global macrocells. In this mode, the EPROM cells are programmed such that the flip-flop in a macrocell is triggered by the dedicated product term and the output buffer is permanently disabled.
Output is permanently enabled
Output is permanently disabled

8. EP1800
Both local and global macrocells can be configured to operate in synchronous or asynchronous mode.
The selection of a particular mode for a local macrocell is done by a single EPROM.
Whereas, the selection of a particular mode for a global macrocells, is done by a 2 EPROM.
All the flip-flops in EP1800 have an individual clear input which is controlled by a dedicated product term.
Like in EP600, each I/O pin in an EP1800 can be configured to provide a combinational output or registered output with or without feedback, and also as an input.