Altera CPLD Max V (P/N: 5M40ZE64C4)

Hi Liam,

Thank you for reaching out to Intel FPGA Community.

To answer your question, MAX V devices allow the device core and I/O blocks to be powered-up with separate supply voltages. . The VCCINT pins supply power to the device core and the VCCIO pins

supply power to the device I/O buffers.

When VCCIO and VCCINT are supplied from different power sources to a MAX V

device, a delay between VCCIO and VCCINT may occur. Normal operation does not

occur until both power supplies are in their recommended operating range. When

VCCINT is powered-up, the IEEE Std. 1149.1 JTAG circuitry is active. TMS and TCK are

connected to VCCIO and if VCCIO is not powered-up, the JTAG signals are left floating.

Thus, any transition on TCK can cause the state machine to transition to an unknown

JTAG state, leading to incorrect operation when VCCIO is finally powered-up. To

disable the JTAG state during the power-up sequence, pull TCK low to ensure that an

inadvertent rising edge does not occur on TCK.