From: Will Sowerbutts <will@sowerbutts.com>
Date: Wed, 25 Jan 2017 14:36:50 +0000 (+0000)
Subject: Kernel: p112: Fix timer interrupt rate
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=2f899edfb6029a60b7d2d4920949b416332833e5;p=FUZIX.git

Kernel: p112: Fix timer interrupt rate
---

diff --git a/Kernel/cpu-z180/z180.s b/Kernel/cpu-z180/z180.s
index c427fec3..967ab13b 100644
--- a/Kernel/cpu-z180/z180.s
+++ b/Kernel/cpu-z180/z180.s
@@ -177,7 +177,7 @@ z180_init_hardware:
         ; set up system tick timer
         xor a
         out0 (TIME_TCR), a
-        ld hl, #(CPU_CLOCK_KHZ * (1000/20) / TICKSPERSEC) ; timer ticks at PHI/20
+        ld hl, #((CPU_CLOCK_KHZ * (1000/Z180_TIMER_SCALE) / TICKSPERSEC) - 1)
         out0 (TIME_RLDR0L), l
         out0 (TIME_RLDR0H), h
         ld a, #0x11         ; enable downcounting and interrupts for timer 0 only
diff --git a/Kernel/platform-p112/kernel.def b/Kernel/platform-p112/kernel.def
index bb1368ac..dfcbfa63 100644
--- a/Kernel/platform-p112/kernel.def
+++ b/Kernel/platform-p112/kernel.def
@@ -14,6 +14,7 @@ Z80_TYPE		    .equ 2
 ; (18.432MHz) but this made the machine unstable.
 USE_FANCY_MONITOR           .equ 1            ; disabling this saves around 0.5KB
 CPU_CLOCK_KHZ               .equ 16000        ; 16MHz is the stock crystal
+Z180_TIMER_SCALE            .equ 10           ; CPU clocks per timer tick
 TICKSPERSEC                 .equ 40           ; timer interrupt rate (Hz)
 
 PROGBASE		    .equ 0x0000