APEX 20K Programmable Logic Device Family Data Sheet
APEX 20KE devices include an enhanced IOE, which drives the FastRow
interconnect. The FastRow interconnect connects a column I/ O pin
directly to the LAB local interconnect within two MegaLAB structures.
This feature provides fast setup times for pins that drive high fan-outs
with complex logic, such as PCI designs. For fast bidirectional I/ O timing,
LE registers using local routing can improve setup times and OE timing.
The APEX 20KE IOE also includes direct support for open-drain
operation, giving faster clock-to-output for open-drain signals. Some
programmable delays in the APEX 20KE IOE offer multiple levels of delay
to fine-tune setup and hold time requirements. The Quartus II software
Compiler can set these delays automatically to minimize setup time while
providing a zero hold time.
Table 11 describes the APEX 20KE programmable delays and their logic
options in the Quartus II software.
Table 11. APEX 20KE Programmable Delay Chains
Programmable Delays
Quartus II Logic Option
Input Pin to Core Delay
Decrease input delay to internal cells
Decrease input delay to input registers
Decrease input delay to output register
Increase delay to output pin
Input Pin to Input Register Delay
Core to Output Register Delay
Output Register t Delay
CO
Clock Enable Delay
Increase clock enable delay
The register in the APEX 20KE IOE can be programmed to power-up high
or low after configuration is complete. If it is programmed to power-up
low, an asynchronous clear can control the register. If it is programmed to
power-up high, an asynchronous preset can control the register. Figure 26
shows how fast bidirectional I/ O pins are implemented in APEX 20KE
devices. This feature is useful for cases where the APEX 20KE device
controls an active-low input or another device; it prevents inadvertent
activation of the input upon power-up.
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Altera Corporation
ETC [ ETC ]
