In-System Programming (ISP) of Actel’s Low-Power Flash Devices Using FlashPro3
v1.1
16- 3
Programming Voltage (VPUMP) and VJTAG
Low-power flash devices support on-chip charge pumps, and therefore require only a single 3.3 V
programming voltage for the VPUMP pin during programming. When the device is not being
programmed, the VPUMP pin can be left floating or can be tied (pulled up) to any voltage between
0 V and 3.6 V. During programming, the target board or the FlashPro3 programmer can provide
VPUMP. FlashPro3 is capable of supplying VPUMP to a single device. If more than one device is to be
programmed using FlashPro3 on a given board, FlashPro3 should not be relied on to supply the
VPUMP voltage.
Low-power flash device I/Os support a bank-based, voltage-supply architecture that simultaneously
supply in a separate bank from the user I/Os, low-power flash devices provide greater flexibility
with supply selection and simplify power supply and printed circuit board (PCB) design. The JTAG
pins can be run at any voltage from 1.5 V to 3.3 V (nominal). Actel recommends that TCK be tied to
GND or VJTAG when not used. This prevents a possible totempole current on the input buffer stage.
For TDI, TMS, and TRST pins, the devices provide an internal nominal 10 k
Ω pull-up resistor. During
programming, all I/O pins, except for JTAG interface pins, are tristated and weakly pulled up to
VCCI. This isolates the part and prevents the signals from floating. The JTAG interface pins are
driven by the FlashPro3 during programming, including the TRST pin, which is driven HIGH.
IEEE 1532 (JTAG) Interface
The supported industry-standard IEEE 1532 programming interface builds on the IEEE 1149.1
(JTAG) standard. IEEE 1532 defines the standardized process and methodology for ISP. Both silicon
and software issues are addressed in IEEE 1532 to create a simplified ISP environment. Any
IEEE 1532–compliant programmer can be used to program low-power flash devices. However, only
limited security and FlashROM features are supported when using the IEEE 1532 standard. The
Actel FlashPro3 programmer was developed exclusively for these devices and will support all the
security and device serialization features. Refer to the standard for detailed information about IEEE
1532.
Security
Unlike SRAM-based FPGAs that require loading at power-up from an external source such as a
microcontroller or boot PROM, Actel nonvolatile devices are live at power-up, and there is no
bitstream required to load the device when power is applied. The unique flash-based architecture
prevents reverse engineering of the programmed code on the device, because the programmed
data is stored in nonvolatile memory cells. Each nonvolatile memory cell is made up of small
capacitors and any physical deconstruction of the device will disrupt stored electrical charges.
Each low-power flash device has a built-in 128-bit Advanced Encryption Standard (AES) decryption
core, except for the 15 k and 30 k gate devices. Any FPGA core or FlashROM content loaded into
the device can optionally be sent as encrypted bitstream and decrypted as it is loaded. This is
Table 16-2 Power Supplies
Power Supply
Programming Mode
Current during
Programming
VCC
1.5 V
< 70 mA
VCCI
1.5 V / 1.8 V / 2.5 V / 3.3 V
(bank-selectable)
I/Os are weakly pulled up.
VJTAG
1.5 V / 1.8 V / 2.5 V / 3.3 V
< 20 mA
VPUMP
3.0 V to 3.6 V
< 80 mA
Note: All supply voltages should be at 1.5 V or higher, regardless of the setting during normal
operation.