The Ultra37000TM family of CMOS CPLDs provides a range of high-density programmable logic solutions with unparalleled system performance. The Ultra37000 family is designed to bring the flexibility, ease of use, and performance of the 22V10 to high-density CPLDs. The architecture is based on a number of logic blocks that are connected by a Programmable Interconnect Matrix (PIM). Each logic block features its own product term array, product term allocator, and 16 macrocells. The PIM distributes signals from the logic block outputs and all input pins to the logic block inputs. All of the Ultra37000 devices are electrically erasable and In-System Reprogrammable (ISR), which simplifies both design and manufacturing flows, thereby reducing costs. The ISR feature provides the ability to reconfigure the devices without having design changes cause pinout or timing changes. The Cypress ISR function is implemented through a JTAG-compliant serial interface. Data is shifted in and out through the TDI and TDO pins, respectively. Because of the superior routability and simple timing model of the Ultra37000 devices, ISR allows users to change existing logic designs while simultaneously fixing pinout assignments and maintaining system performance. The entire family features JTAG for ISR and boundary scan, and is compatible with the PCI Local Bus specification, meeting the electrical and timing requirements. The Ultra37000 family features user programmable bus-hold capabilities on all I/Os.