diff --git a/.github/synthesis/staging.json b/.github/synthesis/staging.json
index cbb1305c2..9a578536b 100644
--- a/.github/synthesis/staging.json
+++ b/.github/synthesis/staging.json
@@ -1,5 +1,6 @@
 [
   {"top": "clockControlDemo0",             "stage": "bitstream"},
-  {"top": "simpleHardwareInTheLoopTest",   "stage": "test"},
-  {"top": "extendedHardwareInTheLoopTest", "stage": "test"}
+  {"top": "extendedHardwareInTheLoopTest", "stage": "test"},
+  {"top": "fdecTest",                      "stage": "test"},
+  {"top": "simpleHardwareInTheLoopTest",   "stage": "test"}
 ]
diff --git a/bittide-instances/bin/Shake.hs b/bittide-instances/bin/Shake.hs
index 2304b66e5..621c912d1 100644
--- a/bittide-instances/bin/Shake.hs
+++ b/bittide-instances/bin/Shake.hs
@@ -38,6 +38,9 @@ import qualified Bittide.Instances.ScatterGather as ScatterGather
 import qualified Bittide.Instances.Si539xSpi as Si539xSpi
 import qualified Bittide.Instances.StabilityChecker as StabilityChecker
 import qualified Bittide.Instances.Synchronizer as Synchronizer
+
+import qualified Bittide.Instances.Tests.FincFdec as FincFdec
+
 import qualified Clash.Util.Interpolate as I
 import qualified Language.Haskell.TH as TH
 import qualified System.Directory as Directory
@@ -199,6 +202,14 @@ defTarget name = Target
   , targetHasTest = False
   }
 
+testTarget :: TH.Name -> Target
+testTarget name = Target
+  { targetName = name
+  , targetHasXdc = True
+  , targetHasVio = True
+  , targetHasTest = True
+  }
+
 enforceValidTarget :: Target -> Target
 enforceValidTarget target@Target{..}
   | targetHasTest && not targetHasVio =
@@ -210,17 +221,7 @@ enforceValidTarget target@Target{..}
 -- | All synthesizable targets
 targets :: [Target]
 targets = map enforceValidTarget
-  [ (defTarget 'BoardTest.simpleHardwareInTheLoopTest)
-    { targetHasXdc = True
-    , targetHasVio = True
-    , targetHasTest = True
-    }
-  , (defTarget 'BoardTest.extendedHardwareInTheLoopTest)
-    { targetHasXdc = True
-    , targetHasVio = True
-    , targetHasTest = True
-    }
-  , defTarget 'Calendar.switchCalendar1k
+  [ defTarget 'Calendar.switchCalendar1k
   , defTarget 'Calendar.switchCalendar1kReducedPins
   , defTarget 'ClockControl.callisto3
   , defTarget 'Counter.counterReducedPins
@@ -235,6 +236,10 @@ targets = map enforceValidTarget
   , defTarget 'Si539xSpi.si5391Spi
   , defTarget 'StabilityChecker.stabilityChecker_3_1M
   , defTarget 'Synchronizer.safeDffSynchronizer
+
+  , testTarget 'BoardTest.extendedHardwareInTheLoopTest
+  , testTarget 'BoardTest.simpleHardwareInTheLoopTest
+  , testTarget 'FincFdec.fdecTest
   ]
 
 shakeOpts :: ShakeOptions
diff --git a/bittide-instances/bittide-instances.cabal b/bittide-instances/bittide-instances.cabal
index 30df26c99..1378c4535 100644
--- a/bittide-instances/bittide-instances.cabal
+++ b/bittide-instances/bittide-instances.cabal
@@ -111,6 +111,8 @@ library
     Bittide.Instances.StabilityChecker
     Bittide.Instances.Synchronizer
 
+    Bittide.Instances.Tests.FincFdec
+
     Clash.Shake.Extra
     Clash.Shake.Flags
     Clash.Shake.Vivado
diff --git a/bittide-instances/data/constraints/fdecTest.xdc b/bittide-instances/data/constraints/fdecTest.xdc
new file mode 100644
index 000000000..04f13dfaf
--- /dev/null
+++ b/bittide-instances/data/constraints/fdecTest.xdc
@@ -0,0 +1,44 @@
+# SPDX-FileCopyrightText: 2022-2023 Google LLC
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# NOTE: This configuration is only valid for the leftmost FPGA in the demo rack.
+#
+# Color   | FPGA pin      | LVLShift      | Connection
+# --------|---------------|---------------|---------
+# Grey    | PMOD0_0       | IO1           | SWDIO
+# Blue    | PMOD0_1       | IO2           | FINC
+# Yellow  | PMOD0_2       | IO3           | MOSI/SDIO
+# Red     | PMOD0_3       | IO4           | SCLK
+# White   | PMOD0_4       | IO5           | SWCLK
+# Purple  | PMOD0_5       | IO6           | FDEC
+# Green   | PMOD0_6       | IO7           | CSB
+# Orange  | PMOD0_7       | IO8           | MISO/SDO
+# Black   | Not connected | Not connected | GND (SWD)
+# Brown   | PMOD_GND      | GND           | GND (SPI)
+#
+# The data wire of the external reset button is connected to PMOD1_3.
+
+
+# CLK_125MHZ
+set_property BOARD_PART_PIN sysclk_125_p [get_ports {CLK_125MHZ_P}]
+set_property BOARD_PART_PIN sysclk_125_n [get_ports {CLK_125MHZ_N}]
+
+# USER_SMA_CLOCK
+set_property -dict {IOSTANDARD LVDS PACKAGE_PIN D23} [get_ports {USER_SMA_CLOCK_P}]
+set_property -dict {IOSTANDARD LVDS PACKAGE_PIN C23} [get_ports {USER_SMA_CLOCK_N}]
+
+# GPIO_LED_0_LS
+set_property BOARD_PART_PIN GPIO_LED_0_LS [get_ports {done}]
+# GPIO_LED_1_LS
+set_property BOARD_PART_PIN GPIO_LED_1_LS [get_ports {success}]
+
+# PMOD0_[0..7]
+# set_property -dict {IOSTANDARD LVCMOS12 PACKAGE_PIN AK25} [get_ports {SWDIO}]
+set_property -dict {IOSTANDARD LVCMOS12 PACKAGE_PIN AN21} [get_ports {FINC}]
+set_property -dict {IOSTANDARD LVCMOS12 PACKAGE_PIN AH18} [get_ports {MOSI}]
+set_property -dict {IOSTANDARD LVCMOS12 PACKAGE_PIN AM19} [get_ports {SCLK}]
+# set_property -dict {IOSTANDARD LVCMOS12 PACKAGE_PIN AE26} [get_ports {SWCLK}]
+set_property -dict {IOSTANDARD LVCMOS12 PACKAGE_PIN AF25} [get_ports {FDEC}]
+set_property -dict {IOSTANDARD LVCMOS12 PACKAGE_PIN AE21} [get_ports {CSB}]
+set_property -dict {IOSTANDARD LVCMOS12 PACKAGE_PIN AM17} [get_ports {MISO}]
diff --git a/bittide-instances/data/tcl/HardwareTest.tcl b/bittide-instances/data/tcl/HardwareTest.tcl
index 268127979..e10cd6fa6 100644
--- a/bittide-instances/data/tcl/HardwareTest.tcl
+++ b/bittide-instances/data/tcl/HardwareTest.tcl
@@ -150,6 +150,7 @@ proc run_single_test {start_probe} {
     # Verify that `done` is not set before starting the test
     set_property OUTPUT_VALUE 0 $start_probe
     commit_hw_vio [get_hw_vios hw_vio_1]
+    after 10
     refresh_hw_vio [get_hw_vios hw_vio_1]
     set done [get_property INPUT_VALUE [get_hw_probes probe_test_done]]
     if {$done != 0} {
diff --git a/bittide-instances/src/Bittide/Instances/MVPs.hs b/bittide-instances/src/Bittide/Instances/MVPs.hs
index b65d9f0e2..74fab24a2 100644
--- a/bittide-instances/src/Bittide/Instances/MVPs.hs
+++ b/bittide-instances/src/Bittide/Instances/MVPs.hs
@@ -4,6 +4,9 @@
 
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE NumericUnderscores #-}
+
+{-# OPTIONS_GHC -fconstraint-solver-iterations=10 #-}
+
 module Bittide.Instances.MVPs where
 
 import Clash.Prelude
diff --git a/bittide-instances/src/Bittide/Instances/Tests/FincFdec.hs b/bittide-instances/src/Bittide/Instances/Tests/FincFdec.hs
new file mode 100644
index 000000000..61422a9c8
--- /dev/null
+++ b/bittide-instances/src/Bittide/Instances/Tests/FincFdec.hs
@@ -0,0 +1,219 @@
+-- SPDX-FileCopyrightText: 2022-2023 Google LLC
+--
+-- SPDX-License-Identifier: Apache-2.0
+
+{-# LANGUAGE NumericUnderscores #-}
+
+-- | A couple of tests testing clock board programming, and subsequently the
+-- FINC and FDEC pins.
+module Bittide.Instances.Tests.FincFdec where
+
+import Clash.Annotations.TH (makeTopEntity)
+import Clash.Explicit.Prelude
+import Clash.Prelude (withClockResetEnable)
+
+import Bittide.Arithmetic.Time
+import Bittide.Counter (domainDiffCounter)
+import Bittide.ClockControl (SpeedChange(NoChange, SlowDown, SpeedUp), speedChangeToFincFdec)
+import Bittide.ClockControl.Si539xSpi (si539xSpi, ConfigState(Finished))
+import Bittide.Instances.Domains
+
+import Clash.Xilinx.ClockGen (clockWizardDifferential)
+
+import Clash.Cores.Xilinx.Extra (ibufds)
+import Clash.Cores.Xilinx.VIO (vioProbe)
+import Clash.Cores.Xilinx.Xpm.Cdc.Single (xpmCdcSingle)
+
+import qualified Bittide.ClockControl.Si5395J as Si5395J
+
+data TestState = Busy | Fail | Success
+data Test = Fdec | Finc
+
+testStateToDoneSuccess :: TestState -> (Bool, Bool)
+testStateToDoneSuccess = \case
+  Busy -> (False, False)
+  Fail -> (True, False)
+  Success -> (True, True)
+
+noReset :: KnownDomain dom => Reset dom
+noReset = unsafeFromHighPolarity (pure False)
+
+eitherReset :: KnownDomain dom => Reset dom -> Reset dom -> Reset dom
+eitherReset (unsafeToHighPolarity -> rstA) (unsafeToHighPolarity -> rstB) =
+  unsafeFromHighPolarity (rstA .||. rstB)
+
+bothReset :: KnownDomain dom => Reset dom -> Reset dom -> Reset dom
+bothReset (unsafeToHighPolarity -> rstA) (unsafeToHighPolarity -> rstB) =
+  unsafeFromHighPolarity (rstA .&&. rstB)
+
+fdecTestGo ::
+  Clock Basic200A ->
+  Reset Basic200A ->
+  Clock Basic200B ->
+  Signal Basic200A Test ->
+  "MISO" ::: Signal Basic200A Bit -> -- SPI
+  "" :::
+    ( Signal Basic200A TestState
+
+    -- Freq increase / freq decrease request to clock board
+    , ( "FINC"    ::: Signal Basic200A Bool
+      , "FDEC"    ::: Signal Basic200A Bool
+      )
+
+      -- SPI to clock board:
+    , "" :::
+      ( "SCLK" ::: Signal Basic200A Bool
+      , "MOSI" ::: Signal Basic200A Bit
+      , "CSB"  ::: Signal Basic200A Bool
+      )
+
+      -- Debug signals:
+    , "" :::
+      ( "SPI_BUSY" ::: Signal Basic200A Bool
+      , "SPI_STATE" ::: Signal Basic200A (BitVector 40)
+      , "SI_LOCKED" ::: Signal Basic200A Bool
+      , "COUNTER_ACTIVE" ::: Signal Basic200A Bool
+      , "COUNTER" ::: Signal Basic200A (Signed 32)
+      )
+    )
+fdecTestGo clk rst clkControlled testSelect miso =
+  (testResult, fIncDec, spiOut, debugSignals)
+ where
+  debugSignals = (spiBusy, pack <$> spiState, siClkLocked, counterActive, counter)
+
+  (_, spiBusy, spiState@(fmap (==Finished) -> siClkLocked), spiOut) =
+    withClockResetEnable clk rst enableGen $
+      si539xSpi
+        Si5395J.testConfig6_200_on_0a_and_0
+        -- Si5395J.testConfigAll200
+        (SNat @(Nanoseconds 1000))
+        (pure Nothing)
+        miso
+
+  rstTest = unsafeFromLowPolarity siClkLocked
+
+  rstControlled =
+    unsafeFromLowPolarity $
+      xpmCdcSingle clk clkControlled $ -- improvised reset syncer
+        unsafeToLowPolarity rst
+
+  (counter, counterActive) =
+    unbundle $
+      -- Note that in a "real" Bittide system the clocks would be wired up the
+      -- other way around: the controlled domain would be the target domain. We
+      -- don't do that here because we know 'rstControlled' will come out of
+      -- reset much earlier than 'rstTest'. Doing it the "proper" way would
+      -- therefore introduce extra complexity, without adding to the test's
+      -- coverage.
+      domainDiffCounter clkControlled rstControlled clk rstTest
+
+  fIncDec = unbundle $ speedChangeToFincFdec clk rst fIncDecRequest
+
+  (fIncDecRequest, testResult) =
+    mealyB clk rstTest enableGen go () (counter, testSelect)
+
+  go :: () -> (Signed 32, Test) -> ((), (SpeedChange, TestState))
+  go () (n, Fdec) = ((), goFdec n)
+  go () (n, Finc) = ((), goFinc n)
+
+
+goFdec :: Signed 32 -> (SpeedChange, TestState)
+goFdec n
+  | n > 20_000  = (NoChange, Fail)
+  | n < -20_000 = (NoChange, Success)
+  | otherwise   = (SlowDown, Busy)
+
+goFinc :: Signed 32 -> (SpeedChange, TestState)
+goFinc n
+  | n > 20_000  = (NoChange, Success)
+  | n < -20_000 = (NoChange, Fail)
+  | otherwise   = (SpeedUp, Busy)
+
+fdecTest ::
+  -- Pins from internal oscillator:
+  "CLK_125MHZ_P" ::: Clock Basic125 ->
+  "CLK_125MHZ_N" ::: Clock Basic125 ->
+
+  -- Pins from clock board:
+  "USER_SMA_CLOCK_P" ::: Clock Basic200B ->
+  "USER_SMA_CLOCK_N" ::: Clock Basic200B ->
+  "MISO" ::: Signal Basic200A Bit -> -- SPI
+
+  "" :::
+    ( "" :::
+      ( "done"    ::: Signal Basic200A Bool
+      , "success" ::: Signal Basic200A Bool
+      )
+
+    -- Freq increase / freq decrease request to clock board
+    , "" :::
+      ( "FINC"    ::: Signal Basic200A Bool
+      , "FDEC"    ::: Signal Basic200A Bool
+      )
+
+      -- SPI to clock board:
+    , "" :::
+      ( "SCLK" ::: Signal Basic200A Bool
+      , "MOSI" ::: Signal Basic200A Bit
+      , "CSB"  ::: Signal Basic200A Bool
+      )
+    )
+fdecTest clkP clkN controlledClockP controlledClockN spiIn =
+  ((testDone, testSuccess), fIncDec, spiOut)
+ where
+  clkControlled = ibufds controlledClockP controlledClockN
+
+  (clk, clkStable0) = clockWizardDifferential (SSymbol @"pll") clkN clkP noReset
+  clkStable1 = xpmCdcSingle clk clk clkStable0 -- improvised reset syncer
+
+  clkStableRst = unsafeFromLowPolarity clkStable1
+  startFdecTestRst = unsafeFromLowPolarity startFdecTest
+  startFincTestRst = unsafeFromLowPolarity startFincTest
+  testRst = eitherReset clkStableRst (bothReset startFdecTestRst startFincTestRst)
+  testRstBool = unsafeToHighPolarity testRst
+
+  (fInc, fDec) = fIncDec
+
+  testF = mux startFdecTest (pure Fdec) (pure Finc)
+
+  (testResult, fIncDec, spiOut, debugSignals) =
+    fdecTestGo clk testRst clkControlled testF spiIn
+
+  (testDone, testSuccess) = unbundle $ testStateToDoneSuccess <$> testResult
+
+  (spiBusy, spiState, siClkLocked, counterActive, counter) = debugSignals
+
+  (startFdecTest, startFincTest) = unbundle $
+    vioProbe
+      (  "probe_test_done"
+      :> "probe_test_success"
+
+      -- Debug signals:
+      :> "probe_clkStable1"
+      :> "probe_testRstBool"
+      :> "probe_spiBusy"
+      :> "probe_spiState"
+      :> "probe_siClkLocked"
+      :> "probe_counterActive"
+      :> "probe_counter"
+      :> "probe_fInc"
+      :> "probe_fDec"
+      :> Nil)
+      ("probe_test_start_fdec" :> "probe_test_start_finc" :> Nil)
+      (False, False)
+      clk
+      testDone
+      testSuccess
+
+      -- Debug signals
+      clkStable1
+      testRstBool
+      spiBusy
+      spiState
+      siClkLocked
+      counterActive
+      counter
+      fInc
+      fDec
+{-# NOINLINE fdecTest #-}
+makeTopEntity 'fdecTest
diff --git a/bittide/src/Bittide/ClockControl.hs b/bittide/src/Bittide/ClockControl.hs
index 4b88350a0..703cef9bb 100644
--- a/bittide/src/Bittide/ClockControl.hs
+++ b/bittide/src/Bittide/ClockControl.hs
@@ -6,6 +6,8 @@
 {-# LANGUAGE NamedFieldPuns #-}
 {-# OPTIONS_GHC -Wno-orphans #-}
 
+{-# OPTIONS_GHC -fconstraint-solver-iterations=10 #-}
+
 -- | Clock controller types and some constants/defaults.
 module Bittide.ClockControl
   ( ClockControlConfig (..)
@@ -16,6 +18,7 @@ module Bittide.ClockControl
   , pessimisticSettleCycles
   , targetDataCount
   , clockPeriodFs
+  , speedChangeToFincFdec
   )
 where
 
@@ -26,7 +29,7 @@ import Data.Proxy (Proxy(..))
 import GHC.Stack (HasCallStack)
 
 import Bittide.Arithmetic.Ppm
-import Bittide.Arithmetic.Time (microseconds)
+import Bittide.Arithmetic.Time (PeriodToCycles, Nanoseconds, Microseconds, microseconds)
 
 import Data.Csv
 
@@ -120,6 +123,56 @@ data SpeedChange
   | NoChange
   deriving (Eq, Show, Generic, ShowX, NFDataX)
 
+data ToFincFdecState
+  = Wait (Unsigned 32)
+  | Pulse (Unsigned 32) SpeedChange
+  | Idle
+  deriving (Generic, NFDataX)
+
+-- | Convert 'SpeedChange' to a pair of (FINC, FDEC). This is currently hardcoded
+-- to work on the Si5395 constraints:
+--
+--   * Minimum Pulse Width: 100 ns
+--   * Update Rate: 1 us
+--
+-- TODO: De-hardcode
+speedChangeToFincFdec ::
+  forall dom .
+  KnownDomain dom =>
+  Clock dom ->
+  Reset dom ->
+  Signal dom SpeedChange ->
+  Signal dom (Bool, Bool)
+speedChangeToFincFdec clk rst =
+  fmap conv . mealy clk rst enableGen go (Wait waitCycles)
+ where
+  pulseCycles :: Unsigned 32
+  pulseCycles =
+    case clockPeriod @dom of
+      SNat -> natToNum @(PeriodToCycles dom (Nanoseconds 100))
+
+  waitCycles :: Unsigned 32
+  waitCycles =
+    case clockPeriod @dom of
+      SNat -> natToNum @(PeriodToCycles dom (Microseconds 1))
+
+  go :: ToFincFdecState -> SpeedChange -> (ToFincFdecState, SpeedChange)
+  go (Wait n) _s
+    | n == 0    = (Idle,         NoChange)
+    | otherwise = (Wait (n - 1), NoChange)
+
+  go (Pulse n s) _s
+    | n == 0    = (Wait waitCycles, s)
+    | otherwise = (Pulse (n - 1) s, s)
+
+  go Idle NoChange = (Idle, NoChange)
+  go Idle s        = (Pulse pulseCycles s, NoChange)
+
+  --               FINC   FDEC
+  conv NoChange = (False, False)
+  conv SpeedUp  = (True,  False)
+  conv SlowDown = (False, True)
+
 instance ToField SpeedChange where
   toField SpeedUp = "speedUp"
   toField SlowDown = "slowDown"
@@ -151,6 +204,7 @@ defClockConfig = ClockControlConfig
   { cccPessimisticPeriod         = pessimisticPeriod
   , cccPessimisticSettleCycles   = pessimisticSettleCycles self
   , cccSettlePeriod              = microseconds 1
+  -- , cccMinimumPulseWidth         = nanoseconds 100
   , cccStepSize                  = stepSize
   , cccBufferSize                = d12 -- 2**12 ~ 4096
   , cccDeviation                 = Ppm 100
diff --git a/bittide/src/Bittide/ClockControl/Si539xSpi.hs b/bittide/src/Bittide/ClockControl/Si539xSpi.hs
index e6c519f43..eeb3642cc 100644
--- a/bittide/src/Bittide/ClockControl/Si539xSpi.hs
+++ b/bittide/src/Bittide/ClockControl/Si539xSpi.hs
@@ -1,9 +1,10 @@
 -- SPDX-FileCopyrightText: 2022-2023 Google LLC
 --
 -- SPDX-License-Identifier: Apache-2.0
-{-# OPTIONS_GHC -fconstraint-solver-iterations=9 #-}
+{-# OPTIONS_GHC -fconstraint-solver-iterations=20 #-}
 
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE UndecidableInstances #-}
 {-# LANGUAGE NamedFieldPuns #-}
 {-# LANGUAGE NumericUnderscores #-}
 {-# LANGUAGE RecordWildCards #-}
@@ -81,28 +82,30 @@ spiCommandToBytes = \case
 
 -- | State of the configuration circuit in 'si539xSpi'.
 data ConfigState dom entries
-  = WaitForReady Bool
+  = WaitForReady Bool -- 0
   -- ^ Continuously read from 'Address' 0xFE at any 'Page', if this operations returns
   -- 0x0F twice in a row, the device is considered to be ready for operation.
-  | ResetDriver Bool
+  | ResetDriver Bool -- 1
   -- ^ Always after a @WaitForReady False@ state, we reset the SPI driver to make sure
   -- it first sets the page and address again.
-  | FetchReg (Index entries)
+  | FetchReg (Index entries) -- 2
   -- ^ Fetches the 'RegisterEntry' at the 'Index' to be written to the @Si539x@ chip.
-  | WriteEntry (Index entries)
+  | WriteEntry (Index entries) -- 3
   -- ^ Writes the 'RegisterEntry' at the 'Index' to the @Si539x@ chip.
-  | ReadEntry (Index entries)
+  | ReadEntry (Index entries) -- 4
   -- ^ Checks if the 'RegisterEntry' at the 'Index' was correctly written to the @Si539x@ chip.
-  | Error (Index entries)
+  | Error (Index entries) -- 5
   -- ^ The 'RegisterEntry' at the 'Index' was not correctly written to the @Si539x@ chip.
-  | WaitForLock
+  | WaitForLock -- 6
   -- ^ Continuously read from 'Address' 0x0C at 'Page' 0x00 until it returns bit 3 is 0.
-  | Finished
+  | Finished -- 7
   -- ^ All entries in the 'Si539xRegisterMap' were correctly written to the @Si539x@ chip.
-  | Wait (Index (PeriodToCycles dom (Milliseconds 300))) (Index entries)
+  | Wait (Index (PeriodToCycles dom (Milliseconds 300))) (Index entries) -- 8
   -- ^ Waits for the Si539X to be calibrated after writing the configuration preamble from 'Si539xRegisterMap'.
   deriving (Show, Generic, NFDataX, Eq)
 
+instance (1 <= entries, KnownNat (DomainPeriod dom), KnownNat entries) => BitPack (ConfigState dom entries)
+
 -- | Utility function to retrieve the entry 'Index' from the 'ConfigState'.
 getStateAddress :: KnownNat entries => ConfigState dom entries -> Index entries
 getStateAddress = \case
@@ -219,7 +222,7 @@ data DriverState dom = DriverState
   -- ^ Current communication transaction.
   , commandAcknowledged :: Acknowledge
   -- ^ Whether or not the current transaction has already been acknowledged.
-  , idleCycles          :: Index (PeriodToCycles dom (Nanoseconds 95))
+  , idleCycles          :: Index (PeriodToCycles dom (Nanoseconds 950))
   -- ^ After communication, slave select must be high for at least 95ns.
   }
   deriving (Generic, NFDataX)