framebuffer/vtg: fix dataflow control (inc. WA for Migen bug - FIXME)

diff --git a/milkymist/framebuffer/__init__.py b/milkymist/framebuffer/__init__.py
index 5800a64f767dfede30886c1bfa5df82e6c699b18..704e08f07fb5555fde727a409f370dfc4552c412 100644 (file)
--- a/milkymist/framebuffer/__init__.py
+++ b/milkymist/framebuffer/__init__.py
@@ -119,15 +119,14 @@ class VTG(Actor):
                                self.token("dac").b.eq(self.token("pixels").b[skip:])
                        ),
                        
-                       generate_en.eq(self.endpoints["timing"].stb & self.endpoints["dac"].ack \
-                               & (~active | self.endpoints["pixels"].stb)),
+                       generate_en.eq(self.endpoints["timing"].stb & (~active | self.endpoints["pixels"].stb)),
                        self.endpoints["pixels"].ack.eq(self.endpoints["dac"].ack & active),
                        self.endpoints["dac"].stb.eq(generate_en)
                ]
                tp = self.token("timing")
                sync = [
                        self.endpoints["timing"].ack.eq(0),
-                       If(generate_en,
+                       If(generate_en & self.endpoints["dac"].ack,
                                hcounter.eq(hcounter + 1),
                        
                                If(hcounter == 0, hactive.eq(1)),
@@ -138,6 +137,8 @@ class VTG(Actor):
                                        hcounter.eq(0),
                                        If(vcounter == tp.vscan,
                                                vcounter.eq(0)
+                                               # FIXME: work around Flow bug
+                                               #self.endpoints["timing"].ack.eq(1)
                                        ).Else(
                                                vcounter.eq(vcounter + 1)
                                        )
@@ -146,10 +147,7 @@ class VTG(Actor):
                                If(vcounter == 0, vactive.eq(1)),
                                If(vcounter == tp.vres, vactive.eq(0)),
                                If(vcounter == tp.vsync_start, self.token("dac").vsync.eq(1)),
-                               If(vcounter == tp.vsync_end,
-                                       self.token("dac").vsync.eq(0),
-                                       self.endpoints["timing"].ack.eq(1)
-                               )
+                               If(vcounter == tp.vsync_end, self.token("dac").vsync.eq(0))
                        )
                ]