(r1) UCInterfaceDocRTLBundles < P1076

P1076 Web>Vhdl2019CollectedRequirements>InterfaceAndBundleEnhancements>UCInterfaceDocRTLBundles (revision 1) (raw view)~~EditAttach~~

---+ 3.2. RTL Design

---++ 3.2.1. Simple Bundles

Connectivity of RTL functions consists of one or more signal objects. A bundle is a simplified form of an interface
that allows this connectivity to be referenced as a single object. As such it is a composite similar in some ways to a
record. One difference is that since a bundle is a port, there must be a method to resolve the IO direction of each
element. Different elements may have a different IO direction.

A simple model for connectivity using bundles is shown below. !SimpleBundleTop is the top level of the design.
B1 and B2 are subblocks of !SimpleBundleTop. SB1 and SB2 are subblocks of B1. SB3 and SB4 are subblocks of
B2. Each connection (labled I1, I2, I3, I4, and I5) is a bundle.

<img src="%ATTACHURLPATH%/IFDocRTLSimpleBundleTop.png" width='520' height='180' />

Within a bundle at any subblock, a given element may be mode in, out, or inout. Bundle elements typically have
different IO modes at opposite ends of the interface. An element of bundle I2 that is mode &#8220;in&#8221; at SB1 will be mode
&#8220;out&#8221; at SB2. Bundle elements typically have same IO modes as the bundle is propagated up or down through the
hierarchy. An element of bundle I3 that is mode &#8220;in&#8221; at SB2 will be mode &#8220;in&#8221; at B1.

---++ 3.2.2. Variant Bundles

The simple view of bundles is that every block connects to every element of the bundle. This is not always the case.
The following example shows potential connectivity of addressable logic. Note that in this case a subblock does not
either drive or read some elements of the interface. In fact some subblocks do not use all bits of some array
elements (note A and DI at B1, B2, and B3). From a synthesis standpoint, having unused elements on a composite
is problematic - they show up as unconnected ports to backend tools. As a result, a method to specify partial
connectivity to a bundle is desirable.

<img src="%ATTACHURLPATH%/IFDocRTLVariantBundles.png" width='850' height='400' />

Attachments

I	Attachment	Action	Size	Date	Who	Comment
png	IFDocRTLSimpleBundleTop.png	manage	14.6 K	2015-07-21 - 14:45	BrentHahoe
png	IFDocRTLVariantBundles.png	manage	43.0 K	2015-07-21 - 14:50	BrentHahoe

Topic revision: r1 - 2016-01-21 - 11:45:44 - TWikiGuest

P1076