© 2000 Scenix Semiconductor, Inc. All rights reserved. 11 SX Device Programming Specifications Rev 2.2 www.scenix.com SX out of synchronization with the programmer. The internal ISP clock will be running at 128KHz
during ISP, if the internal clock is trimmed at 4MHz. 2.12 Programming the Customer ID There are 16 12-bit words location available for programming the customer ID. These ID words are
located after the program memory space. If the size of the program memory is 2K, then the last address
of the program memory is $7FF and the addresses of the customer ID words are from $800 to $80F. If
only the first page (512 words) is used for the program memory, then the last address of the program
memory is $1FF and the addresses of the ID words are from $200 to $20F, and so on. These words
outside of the program memory are only accessible during the programming mode. 2.13 Programming the PINS Bit Bit 10 in the FUSEX word of SX18/20/28 is used to identify the number of pins in the package. For
the 28 pin device, this bit should be programmed to 1. For the 18/20 pins package, this bit should be
programmed to 0. The chip will not be programmed, if this bit is not programmed correctly first. 2.14 Exiting the ISP Mode Exiting  from  the  ISP  mode  must  be  done  according  to  the  following  protocol  to  prevent  possible damage to system components: 1.   The programmer drops the voltage on the OSC1 pin from the programming voltage to logic zero. This is a signal to exit from the ISP mode. 2.   On the next rising clock edge after the sync cycle, the SX device exits from the ISP mode and generates an internal reset signal that resets the device. The programmer must observe the same
protocol until the end of this step. 3.   The programmer releases the OSC1 pin, allowing the SX device to begin normal operation. 4.