From 343dd83cdd32831f19bd41bd78d254964c0b2573 Mon Sep 17 00:00:00 2001
From: mgcaret <mgcaret@users.noreply.github.com>
Date: Sat, 14 Dec 2019 14:41:23 -0800
Subject: [PATCH] Neon816: VDC access words

---
 platforms/Neon816/Neon816-hw.inc |  2 +-
 platforms/Neon816/platform-lib.s | 48 ++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/platforms/Neon816/Neon816-hw.inc b/platforms/Neon816/Neon816-hw.inc
index 9dc48fc..0957fe1 100644
--- a/platforms/Neon816/Neon816-hw.inc
+++ b/platforms/Neon816/Neon816-hw.inc
@@ -91,7 +91,7 @@ SPI2ctrl3 = $10001F               ; init = $05
 ; VDC
 ; *****************
 
-VDCio     = $100120               ; read: 1 byte, write: 1 or 2 bytes
+VDCbase   = $100120               ; base address, there are $20 registers
 
 ; *****************
 ; FDC
diff --git a/platforms/Neon816/platform-lib.s b/platforms/Neon816/platform-lib.s
index 1315fc2..95ef8dd 100644
--- a/platforms/Neon816/platform-lib.s
+++ b/platforms/Neon816/platform-lib.s
@@ -209,6 +209,54 @@ dword     I2C2_FETCH,"I2C2@+"
           .a16
 eword
 
+dword     VDC_C_STORE,"VDCC!"
+          jsr   _popay            ; pop offset
+          phy                     ; save low word
+          jsr   _popay            ; pop value to write
+          pla                     ; get offset back
+          phx                     ; save SP
+          tax                     ; offset to x reg
+          sep   #SHORT_A          ; whew! that was fun!
+          .a8
+          tya                     ; value to A
+          sta   f:VDCbase,x
+          rep   #SHORT_A
+          .a16
+          plx                     ; restore SP
+          NEXT
+eword
+
+dword     VDC_C_FETCH,"VDCC@"
+          jsr   _popay            ; pop offet
+          phx                     ; save SP
+          tya
+          tax
+          sep   #SHORT_A          ; whew! that was fun!
+          .a8
+          lda   f:VDCbase,x
+          rep   #SHORT_A
+          .a16
+          plx                     ; restore SP
+          and   #$00FF
+          tay
+          lda   #$0000
+          PUSHNEXT
+eword
+
+dword     VDC_STORE,"VDC!"
+          jsr   _popay            ; again! again! again!
+          phy
+          jsr   _popay
+          pla
+          phx
+          tax
+          tya
+          sta   f:VDCbase,x
+          rep   #SHORT_A
+          .a16
+          plx                     ; restore SP
+          NEXT
+eword
 
 dend