EPC16UC88N Datasheet, PDF (25/36 Pages) Altera Corporation – Enhanced Configuration (EPC) Devices Datasheet

Power-On Reset
Page 25
Table 10. JTAG Interface Pins and Other Required Controller Pins (Part 2 of 2)
Pin Name
EXCLK
PORSEL
TM0
TM1
Pin Type
Input
Input
Input
Input
Description
Optional external clock input pin that can be used to generate the configuration
clock (DCLK).
When an external clock source is not used, connect this pin to a valid logic level
(high or low) to prevent a floating-input buffer. If EXCLK is used, toggling the
EXCLK input pin after the FPGA enters user mode will not effect the EPC device
operation.
This pin selects a 2-ms or 100-ms POR counter delay during power up. When
PORSEL is low, POR time is 100 ms. When PORSEL is high, POR time is 2 ms.
This pin must be connected to a valid logic level.
For normal operation, this test pin must be connected to GND.
For normal operation, this test pin must be connected to V_CC.
Power-On Reset
The POR circuit keeps the system in reset until power-supply voltage levels have
stabilized. The POR time consists of the V_CC ramp time and a user-programmable
POR delay counter. When the supply is stable and the POR counter expires, the POR
circuit releases the OE pin. The POR time can be further extended by an external
device by driving the OE pin low.
1 Do not execute JTAG or ISP instructions until POR is complete.
The EPC device supports a programmable POR delay setting. You can set the POR
delay to the default 100-ms setting or reduce the POR delay to 2 ms for systems that
require fast power-up. The PORSEL input pin controls this POR delay—a logic-high
level selects the 2-ms delay, while a logic-low level selects the 100-ms delay.
The EPC device enters reset under the following conditions:
■ The POR reset starts at initial power-up during V_CC ramp-up or if V_CC drops
below the minimum operating condition anytime after V_CC has stabilized
■ The FPGA initiates reconfiguration by driving nSTATUS low, which occurs if the
FPGA detects a CRC error or if the FPGA’s nCONFIG input pin is asserted
■ The controller detects a configuration error and asserts OE to begin reconfiguration
of the Altera FPGA (for example, when CONF_DONE stays low after all configuration
data has been transmitted)
January 2012 Altera Corporation
Enhanced Configuration (EPC) Devices Datasheet