Issue
141 March 2002
You
Too Can Design with SoC
A
Design Challenge 2002 Primer
byJeff
Bachiochi
Interrupts
Of the 15 interrupts
(excluding reset) in the vector table of a CY8C2xxx device,
12 are associated with the analog and digital blocks (see
Table 1). The other three interrupts
come from the SMV, sleep timer, and general-purpose I/O
pins. Of the 12 PSoC interrupts, four come from the Acolumn
x analog block column outputs. Eight interrupts come from
the digital PSoC blocks.
Two interrupt
mask registers (INT_MSK0/1) allow each of these sources
to be enabled and disabled separately. A separate register,
INT_VC, holds the highest priority pending interrupt.
(Warning: Writing to this register clears all pending
interrupts!) The GPIO interrupt vector is an OR of all
enabled port bit activated interrupts. This could get
confusing when you’re figuring out where the interrupt(s)
came from.
PSoC blocks
Programmable
System-on-a-Chip blocks are user-configurable system resources.
The PSoC from Cypress includes eight digital and 12 analog
PSoC blocks. These are configured using PSoC designer
software. Not only will the designer software help in
the configuration process, but will also prepare a device
datasheet unique to your configuration.
Many of the
digital block functions may be included in today’s microcontrollers,
but the ability to configure the function of each block
allows you to include multiples of the same function for
those special applications. Including analog functions
in a microcontroller is not a new idea, but the CY8C2xxx
analog blocks include devices not previously available
on a microcontroller. Let’s take a closer look at both
of these types of PSoC blocks.
