From: Cassie Jones Date: Mon, 3 Feb 2020 07:27:35 +0000 (-0500) Subject: Add the wait state to the state machine X-Git-Url: https://git.witchoflight.com/jade-rose/commitdiff_plain Add the wait state to the state machine The implementation of the WAIT state currently constantly reads from memory at the WAIT-ed address, resuming when a nonzero value comes back. It might be better to have specific support for that in an interrupt controller type of hardware which would send notifications when the appropriate address changed. --- diff --git a/hardware/core.py b/hardware/core.py index 7a2fdc1..1e02cb4 100644 --- a/hardware/core.py +++ b/hardware/core.py @@ -7,6 +7,7 @@ class CpuState(Enum): EXEC = 1 EXEC2 = 2 HALT = 3 + WAIT = 4 class Core(Elaboratable): @@ -53,6 +54,20 @@ class Core(Elaboratable): with m.Elif(self.state == CpuState.EXEC2): m.d.sync += self.state.eq(CpuState.READ) self.execute2(m, self.inst, self.d_in) + with m.Elif(self.state == CpuState.WAIT): + # This should be changed to avoid reading from memory every cycle + # for power purposes. Instead in the wait state we should just + # leave the address line set and the output line high, and let an + # external interrupt controller send back a wake signal. + m.d.comb += self.addr.eq(Cat(self.it, self.data1)) + m.d.comb += self.r_en.eq(True) + with m.If(self.d_in): + m.d.sync += self.state.eq(CpuState.READ) + m.d.comb += [ + self.r_en.eq(False), + self.w_en.eq(True), + self.d_out.eq(self.d_in - 1), + ] return m def execute(self, m, inst): @@ -63,12 +78,18 @@ class Core(Elaboratable): with m.Case("00000001"): # NOPE pass with m.Case("00000010"): # PRNT - m.d.comb += self.debug.eq(self.it) - m.d.comb += self.debug_en.eq(True) + m.d.comb += [ + self.debug.eq(self.it), + self.debug_en.eq(True), + ] with m.Case("00000011"): # WAIT - pass # @TODO: Implement WAIT + m.d.sync += self.state.eq(CpuState.WAIT) + m.d.comb += [ + self.addr.eq(Cat(self.it, self.data1), + self.r_en.eq(True), + ] with m.Case("0000010-"): # reserved - pass + m.d.sync += self.state.eq(CpuState.HALT) with m.Case("00000110"): # CABA pass # @TODO: Implement CABA with m.Case("00000111"): # COFA