HC4GX15 Datasheet, PDF (140/668 Pages) Altera Corporation – HardCopy IV Device Handbook

9–2
Chapter 9: Hot Socketing and Power-On Reset in HardCopy IV Devices
Hot-Socketing Feature Implementation in HardCopy IV Devices
I/O Pins Remain Tri-Stated During Power-Up
A device that does not support hot socketing may interrupt system operation or cause
contention by driving out before or during power-up. In a hot-socketing situation, the
HardCopy IV device’s output buffers are turned off during system power-up or
power-down. Also, the HardCopy IV device does not drive out until the device is in
user mode and working within recommended operating conditions.
Insertion or Removal of a HardCopy IV Device from a Powered-Up System
Devices that do not support hot socketing can short power supplies when powered
up through the device signal pins. This irregular power-up can damage both the
driving and driven devices and can disrupt card power-up.
A HardCopy IV device may be inserted into (or removed from) a powered-up system
board without damaging or interfering with system board operation. You can
power-up or power-down all power supplies in any sequence, as long as they are all
ramped up to full rail before the HardCopy IV device starts to communicate with
other devices on the board. This requirement is discussed in “Power-On Reset
Circuitry” on page 9–3. HardCopy IV devices are immune to latch-up when
performing hot socketing.
Hot-Socketing Feature Implementation in HardCopy IV Devices
The hot-socketing feature turns off the output buffer during power-up and
power-down of the V_CC, V_CCIO, V_CCPGM, or V_CCPD power supplies. Each I/O pin has the
circuitry shown in Figure 9–1.
Figure 9–1. Hot-Socketing Circuit Block Diagram for HardCopy IV Devices
V_CCIO
Power On
Reset
Monitor
Weak
R
Pull-Up
Resistor
PAD
Output Enable
Voltage
Tolerance
Control
Hot Socket
Output
Pre-Driver
Input Buffer
to Core Logic
HardCopy IV Device Handbook, Volume 1
© December 2008 Altera Corporation