SX Device Programming Specifications Rev 2.2 2 © 2000 Scenix Semiconductor, Inc. All rights reserved. www.scenix.com 1.0 Introduction The SX device has a program memory consisting of 2,048 (SX28) or 4,096 (SX52) words of 12 bits
per word, plus some additional 12-bit words that specify the device configuration. This memory is a
non-volatile, electrically erasable (EEPROM) flash memory, rated for 10,000 rewrite cycles. Before you can use the SX device, you must write the application code into the program memory. You
do this by placing the device into a programming mode and following the protocol for accessing the
program memory. You can write to the program memory only in the programming mode, not when the
device is executing the application software. 1.1 Erasure and Reprogramming When you erase the program memory, you automatically erase the entire memory, including the FUSE
word, and FUSEX word registers. An erased memory has all bits set to 1. When you program the
device, you clear some of the bits to 0. If you want to reprogram a memory location and clear some
more bits to 0, you can “overwrite” the memory location without erasing. However, if you want to
program a bit to 1 that has already been cleared to 0, the only way to do so is to erase and reprogram
the whole EEPROM memory. Parts shipped to the customer are not erased. So erase the part before
programming. Specification for the Erase Time is 500 ms (VCC = 5V, Room temp). 1.2 In-System and Parallel Programming Modes There are two basic device programming modes, called the “In-System Programming” (ISP) mode and
the “parallel” mode. The In-System Programming mode uses just two device pins, OSC1, and OSC2,
and writes the data to the device serially, one bit at a time. This mode lets you program devices that
are already installed in the target system. The parallel mode uses a larger set of pins and writes data 12
bits at a time, in parallel. This mode is a little faster but can only be used to program free-standing SX
parts, because it uses device I/O pins to program the part. 2.0 In-System Programming (ISP) Mode The In-System Programming (ISP) mode lets you program or re-program an SX device that has been
installed and soldered into the target system. Using the ISP mode has many advantages over traditional
programming methods, in all stages of the product life: development, manufacturing, and customer
service. In the product development cycle, a separate “emulation” type device is not required. The controller
device used for development is the same as the one used for final production, including the package
type and pinout. The SX device can be soldered into the target system, and then programmed and
reprogrammed any number of times, without removing and reinstalling it. No special socket or support
circuitry is required, so the system can be debugged accurately, even in timing-sensitive and noise-
sensitive applications. For manufacturing, circuit boards can be pre-built with the controller installed and soldered on the
board,  even  before  the  software  has  been  finalized,  to  meet  short  time-to-market  requirements.