The CY7C637xxC is an 8-bit RISC one-time-programmable
(OTP) microcontroller. The instruction set has been optimized
specifically for USB and PS/2 operations, although the microcontrollers
can be used for a variety of other embedded applications.
The CY7C637xxC features up to 16 GPIO pins to support
USB, PS/2 and other applications. The I/O pins are grouped
into two ports (Port 0 to 1) where each pin can be individually
configured as inputs with internal pull-ups, open drain outputs,
or traditional CMOS outputs with programmable drive strength
of up to 50 mA output drive. Additionally, each I/O pin can be
used to generate a GPIO interrupt to the microcontroller. Note
the GPIO interrupts all share the same “GPIO” interrupt vector.
The CY7C637xxC microcontrollers feature an internal oscillator.
With the presence of USB traffic, the internal oscillator
can be set to precisely tune to USB timing requirements (6
MHz ±1.5%). Optionally, an external 6-MHz ceramic resonator
can be used to provide a higher precision reference for USB
operation. This clock generator reduces the clock-related
noise emissions (EMI). The clock generator provides the 6-
and 12-MHz clocks that remain internal to the microcontroller.
The CY7C637xxC has 8 Kbytes of EPROM and 256 bytes of
data RAM for stack space, user variables, and USB FIFOs.
These parts include low-voltage reset logic, a Watchdog timer,
a vectored interrupt controller, a 12-bit free-running timer, and
capture timers. The low-voltage reset (LVR) logic detects
when power is applied to the device, resets the logic to a
known state, and begins executing instructions at EPROM
address 0x0000. LVR will also reset the part when VCC drops
below the operating voltage range. The Watchdog timer can
be used to ensure the firmware never gets stalled for more
than approximately 8 ms.