intr_timing.lisp

 Copyright (C) 2017 Joonas Javanainen <[email protected]>
;
; Permission is hereby granted, free of charge, to any person obtaining a copy
; of this software and associated documentation files (the "Software"), to deal
; in the Software without restriction, including without limitation the rights
; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
; copies of the Software, and to permit persons to whom the Software is
; furnished to do so, subject to the following conditions:
; 
; The above copyright notice and this permission notice shall be included in
; all copies or substantial portions of the Software.
;   
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
; SOFTWARE.

; Tests when interrupts are checked during the fetch cycle (M1)

(define (pulse-sclk)
  (do
    (set-output-value :sclk false)
    (sleep-ns 100)
    (sample-pins)
    (set-output-value :sclk true)
    (sleep-ns 100)
    (sample-pins)))
  
; This function sets up a serial interrupt so that it can be triggered with a
; single sclk pulse
(define (prepare-test)
  (do
    (reset-avoid-bootrom)
  
    ; Use VRAM as stack to safely use the data bus at all times
    ; ld sp, $8fff
    (inject-data 0x31)
    (inject-data 0xff)
    (inject-data 0x8f)
  
    ; ei
    (inject-data 0xfb)
  
    ; ld a, $80
    (inject-data 0x3e)
    (inject-data 0x80)
  
    ; ldh (<SC), a
    (inject-data 0xe0)
    (inject-data 0x02)
    (step-clock-edges 8)

    ; ld a, $08
    (inject-data 0x3e)
    (inject-data 0x08)

    (set-output-value :sclk true)
    (set-output-enable :sclk true)
    (dotimes 7 (pulse-sclk))

    ; ldh (<IE), a
    (inject-data 0xe0)
    (inject-data 0xff)
    (step-clock-edges 8)

    ; Output NOPs so we won't have to inject them manually
    (set-output-value :data 0x00)
    (set-output-enable :data 0xff)))

(define (assert-first-stack-push-cycle) 
  (do
    (step-clock-edges 2)
    (assert-pins :maddr 0x0ffe)
    (step-clock-edges 6)))

(define (assert-second-stack-push-cycle)
  (do
    (step-clock-edges 2)
    (assert-pins :maddr 0x0ffd)
    (step-clock-edges 6)))

(do
  (for 1 5 (lambda (n)
    (do
      (prepare-test)

      (step-clock-edges n)
      (pulse-sclk)
      (step-clock-edges (- 8 n))

      ; Standard delay of 2 M-cycles
      (step-clock-edges 16)

      (assert-first-stack-push-cycle)
      (assert-second-stack-push-cycle))))

  (for 5 9 (lambda (n)
    (do
      (prepare-test)

      (step-clock-edges n)
      (pulse-sclk)
      (step-clock-edges (- 8 n))

      ; Standard delay of 2 M-cycles
      (step-clock-edges 16)

      ; This time there's one more M-cycle before the stack pushes
      (step-clock-edges 8)
      
      (assert-first-stack-push-cycle)
      (assert-second-stack-push-cycle)))))