Update on MKHBC-8-Rx : NV RAM access added to DS1685 driver.

DS1685 chip has non-volatile (battery sustained) RAM in two banks. Total of 242 bytes are available for user to store data or code that will be persistent between system power cycles (assuming external 3V battery is used).
I have plans regarding this memory for future iterations of the operating system, so right after I finished the RTC / BRAM card I got to working on enhancing the driver to have read / write access to this memory.

The new API:

/*
 * File: mkhbcos_ds1685.h
 * Purpose: Declarations and definitions for
 *          DS1685 RTC (Real Time Clock) chip API.
 * Author: Marek Karcz
 * Created: 02/05/2012
 *
 * Revision history:
 *
 *
 */

#ifndef MKHBCOS_DS1685
#define MKHBCOS_DS1685

// DS RTC registers mask bits

// reg. A

#define DSC_REGA_UIP 0x80 // %10000000
#define DSC_REGA_DV2 0x40 // %01000000
#define DSC_REGA_DV1 0x20 // 100000
#define DSC_REGA_DV0 0x10 // 010000
#define DSC_REGA_RS3 0x08 // 001000
#define DSC_REGA_RS2 0x04 // 000100
#define DSC_REGA_RS1 0x02 // 000010
#define DSC_REGA_RS0 0x01 // 000001

// aliases

#define DSC_REGA_CTDWN DSC_REGA_DV2
#define DSC_REGA_OSCEN DSC_REGA_DV1
#define DSC_REGA_BSEL DSC_REGA_DV0
#define DSC_REGA_BANK0 0xEF
#define DSC_REGA_BANK1 0x10

// reg. B

#define DSC_REGB_SET 0x80 // %10000000
#define DSC_REGB_PIE 0x40 // %01000000
#define DSC_REGB_AIE 0x20 // 100000
#define DSC_REGB_UIE 0x10 // 010000
#define DSC_REGB_SQWE 0x08 // 001000
#define DSC_REGB_DM 0x04 // 000100
#define DSC_REGB_24o12 0x02 // 000010
#define DSC_REGB_DSE 0x01 // 000001

// aliases

#define DSC_REGB_UNSET 0x7F // %01111111


struct ds1685_clkdata
{
unsigned char seconds;
unsigned char minutes;
unsigned char hours;
unsigned char dayofweek;
unsigned char date; // day
unsigned char month;
unsigned char year;
unsigned char century;
};

unsigned char __fastcall__ ds1685_init (unsigned char regb,
                                        unsigned char rega,
                                        unsigned char regextb,
                                        unsigned char regexta);

struct ds1685_clkdata *ds1685_rdclock (struct ds1685_clkdata *buf);
void ds1685_setclock (struct ds1685_clkdata *buf);
void ds1685_settime (struct ds1685_clkdata *buf);
/* bank - 0 or 1, addr - $00 - $7f ($0e - $7f for Bank 0), data - 0..255 */
void ds1685_storeram (unsigned char bank,
              unsigned char addr,
      unsigned char data);  
unsigned char __fastcall__ ds1685_readram(unsigned char bank,
                         unsigned char addr);

#endif

and the code:

;------------------------------------------------------------------
;
; File: mkhbcos_ds1685.s
; Author: Marek Karcz
; Purpose: Implements initialization routines and API for
; Real Time Clock chip DS1685 with multiplexed
;           address bus connected to buffered I/O bus as an I/O
;           device.
;
; Revision history:
; 2012-01-31:
; Initial revision.
;       (NOTE: These routines will eventually make their way
;              to EPROM as a part of firmware. At that time,
;              this file will be revised to call up the API
;              functions in the kernal table, instead of
;              being full implementation.)
;
; 2012-02-06:
; Implementation.
;
; 2015-11-29
;   I/O slot assignment changed.
;
; 2015-12-5
;   Modification due to hardware changes (Chris Ward variant):
;   DSCALADDR and DSCALDATA order changed.
;
; 2017-06-15:
;    Added functions to store and read non-volatile RAM.
;
;------------------------------------------------------------------

; M.O.S. API defines (kernal)

.define mos_StrPtr $E0
.define tmp_zpgPt $F6
.define IOBase $C000
.define RTC IOBase+256
;.define RTC IOBase+7*256

.define DSCALADDR RTC
.define DSCALDATA RTC+1

.setcpu "6502"
.import ldaxysp,pushax,popax,pusha,popa,staspidx
.import incsp2,incsp3,incsp4,ldauidx

.define sp $20

;RegB = tmp_zpgPt
;RegA = tmp_zpgPt+1
;RegXB = tmp_zpgPt+2
;RegXA = tmp_zpgPt+3
;RegC = tmp_zpgPt+4
;Temp = tmp_zpgPt+5

;BankNum = tmp_zpgPt
;RamAddr = tmp_zpgPt+1
;RamVal  = tmp_zpgPt+2 

.segment "DATA"

RegB:    .byte $00
RegA:    .byte $00
RegXB:   .byte $00
RegXA:   .byte $00
RegC:    .byte $00
Temp:    .byte $00
BankNum: .byte $00
RamAddr: .byte $00
RamVal:  .byte $00

ExtRamAddr = $50
ExtRamPort = $53

; DS RTC registers mask bits

; reg. A
DSC_REGA_UIP = %10000000
DSC_REGA_DV2 = %01000000
DSC_REGA_DV1 = 100000
DSC_REGA_DV0 = 010000
DSC_REGA_RS3 = 001000
DSC_REGA_RS2 = 000100
DSC_REGA_RS1 = 000010
DSC_REGA_RS0 = 000001
; aliases
DSC_REGA_CTDWN = DSC_REGA_DV2
DSC_REGA_OSCEN = DSC_REGA_DV1
DSC_REGA_BSEL = DSC_REGA_DV0
DSC_REGA_BANK0 = $EF
DSC_REGA_BANK1 = $10

; reg. B
DSC_REGB_SET = %10000000
DSC_REGB_PIE = %01000000
DSC_REGB_AIE = 100000
DSC_REGB_UIE = 010000
DSC_REGB_SQWE = 001000
DSC_REGB_DM = 000100
DSC_REGB_24o12 = 000010
DSC_REGB_DSE = 000001

; aliases

DSC_REGB_UNSET = %01111111


; code

.export _ds1685_init,_ds1685_rdclock,_ds1685_setclock,_ds1685_settime
.export _ds1685_readram,_ds1685_storeram
;,_read

.segment "CODE"

; Initialize DS1685 RTC chip.
; unsigned char __fastcall__ ds1685_init (unsigned char regb,
;                                         unsigned char rega,
;                                         unsigned char regextb,
;                                         unsigned char regexta)

.proc _ds1685_init: near

.segment "CODE"
; get parameters, put them in temp. buffer
jsr pusha
ldy #$03
;ldx #$00
lda (sp),y
sta RegB
ldy #$02
;ldx #$00
lda (sp),y
sta RegA
ldy #$01
;ldx #$00
lda (sp),y
sta RegXB
ldy #$00
;ldx #$00
lda (sp),y
sta RegXA
; initialize control register B
ldx RegB
lda #$0b
jsr WrRTC
; read status register C
lda #$0c
jsr RdRTC
sta RegC
; initialize control register A, switch to bank 1
lda RegA
ora #DSC_REGA_BANK1 ; switch to bank 1
tax
lda #$0a
jsr WrRTC
; initialize extended control register B
ldx RegXB
lda #$4b
jsr WrRTC
; initialize extended control register A
ldx RegXA
lda #$4a
jsr WrRTC
; switch to bank 0
  jsr Switch2Bank0
ldx #$00
lda RegC
  jsr incsp4
rts

.endproc

.segment "CODE"

; read clock data
; struct ds1685_clkdata *ds1685_rdclock(struct ds1685_clkdata *buf);
; struct ds1685_clkdata
; {
; unsigned char seconds;
; unsigned char minutes;
; unsigned char hours;
; unsigned char dayofweek;
; unsigned char date; // day
; unsigned char month;
; unsigned char year;
; unsigned char century;
; };

.proc _ds1685_rdclock:near

.segment "CODE"
; disable update transfers

lda #$0b
jsr RdRTC
sta RegB ; save register B for later
ora #DSC_REGB_SET
tax
lda #$0b
jsr WrRTC


; determine mode (BCD or BIN)

lda #DSC_REGB_DM
sta Temp
lda RegB
bit Temp
bne binmoderead

; can't do BCD mode yet, return
ldy #$01
jsr ldaxysp
jsr incsp2
rts

binmoderead:
; binary mode read

lda #$00 ; load register address of seconds
jsr RdRTC ; read register value to Acc
and #111111 ; mask 2 upper bits
ldy #$00
jsr Tfer2RetBuf ; transfer to return buffer at index 0 (seconds)

lda #$02 ; load register address of minutes
jsr RdRTC ; read register value to Acc
and #111111 ; mask 2 upper bits
ldy #$01
jsr Tfer2RetBuf ; transfer to return buffer at index 1 (minutes)

lda #$04 ; load register address of hours
jsr RdRTC ; read register value to Acc
pha
lda #DSC_REGB_24o12
sta Temp
lda RegB ; determine which hours mode (12/24 hours)
bit Temp
beq mode12hbin
pla
and #011111 ; mask 3 upper bits for 24H mode read
clc
bcc storehours
mode12hbin:
pla
and #001111 ; mask 4 upper bits for 12H mode read
storehours:
ldy #$02
jsr Tfer2RetBuf ; transfer to return buffer at index 2 (hours)

lda #$06 ; load register address of day (of week)
jsr RdRTC ; read register value to Acc
and #000111 ; mask 5 upper bits
ldy #$03
jsr Tfer2RetBuf ; transfer to return buffer at index 3 (dayofweek)

lda #$07 ; load register address of date (day of month)
jsr RdRTC ; read register value to Acc
and #011111 ; mask 3 upper bits
ldy #$04
jsr Tfer2RetBuf ; transfer to return buffer at index 4 (date)

lda #$08 ; load register address of month
jsr RdRTC ; read register value to Acc
and #001111 ; mask 4 upper bits
ldy #$05
jsr Tfer2RetBuf ; transfer to return buffer at index 5 (month)

lda #$09 ; load register address of year
jsr RdRTC ; read register value to Acc
and #%011111111 ; mask the highest bit
ldy #$06
jsr Tfer2RetBuf ; transfer to return buffer at index 6 (year)

  jsr Switch2Bank1

lda #$48 ; load register address of century
jsr RdRTC ; read register value to Acc
ldy #$07
jsr Tfer2RetBuf ; transfer to return buffer at index 7 (century)

  jsr Switch2Bank0

; enable update transfers

lda #$0b
jsr RdRTC
and #DSC_REGB_UNSET
tax
lda #$0b
jsr WrRTC

ldy #$01
jsr ldaxysp
jsr incsp2
rts

.endproc


.segment "CODE"

; set clock data
; void ds1685_setclock (struct ds1685_clkdata *buf);

.proc _ds1685_setclock:near

.segment "CODE"
; disable update transfers
; set binary mode
lda #$0b
jsr RdRTC
ora #DSC_REGB_SET
ora #DSC_REGB_DM
tax
lda #$0b
jsr WrRTC

ldy #$00 ; get argument 0 (seconds)
jsr GetParFromSpIdx
tax
lda #$00 ; write to DS1685 seconds register
jsr WrRTC

ldy #$01 ; get argument 1 (minutes)
jsr GetParFromSpIdx
tax
lda #$02 ; write to DS1685 minutes register
jsr WrRTC

ldy #$02 ; hours
jsr GetParFromSpIdx 
tax
lda #$04
jsr WrRTC

ldy #$03 ; day of week
jsr GetParFromSpIdx
tax
lda #$06
jsr WrRTC

ldy #$04 ; date (day of month)
jsr GetParFromSpIdx
tax
lda #$07
jsr WrRTC

ldy #$05 ; month
jsr GetParFromSpIdx
tax
lda #$08
jsr WrRTC

ldy #$06 ; year
jsr GetParFromSpIdx
tax
lda #$09
jsr WrRTC

; enable update transfers

lda #$0b
jsr RdRTC
and #DSC_REGB_UNSET
tax
lda #$0b
jsr WrRTC
; disable update transfers
lda #$0b
jsr RdRTC
ora #DSC_REGB_SET
tax
lda #$0b
jsr WrRTC

lda #$0a ; get reg. A
jsr RdRTC
ora #DSC_REGA_BANK1 ; switch to bank 1
tax
lda #$0a
jsr WrRTC

ldy #$07 ; century
jsr GetParFromSpIdx
tax
lda #$48
jsr WrRTC

  jsr Switch2Bank0

; enable update transfers

lda #$0b
jsr RdRTC
and #DSC_REGB_UNSET
tax
lda #$0b
jsr WrRTC

jsr incsp2

rts

.endproc

.segment "CODE"

; set clock data
; void ds1685_settime (struct ds1685_clkdata *buf);

.proc _ds1685_settime:near

.segment "CODE"
  jsr Switch2Bank0

; disable update transfers
; set binary mode
lda #$0b
jsr RdRTC
ora #DSC_REGB_SET
ora #DSC_REGB_DM
tax
lda #$0b
jsr WrRTC

ldy #$00 ; get argument 0 (seconds)
jsr GetParFromSpIdx
tax
lda #$00 ; write to DS1685 seconds register
jsr WrRTC

ldy #$01 ; get argument 1 (minutes)
jsr GetParFromSpIdx
tax
lda #$02 ; write to DS1685 minutes register
jsr WrRTC

ldy #$02 ; hours
jsr GetParFromSpIdx 
tax
lda #$04
jsr WrRTC

; enable update transfers

lda #$0b
jsr RdRTC
and #DSC_REGB_UNSET
tax
lda #$0b
jsr WrRTC

jsr incsp2

rts

.endproc

.segment "CODE"

; store value in non-volatile RAM
; void ds1685_storeram (unsigned char bank,
;                 unsigned char addr,
;         unsigned char data);

.proc _ds1685_storeram: near

.segment "CODE"
; get parameters, put them in temp. buffer
;jsr pusha
ldy #$02
;ldx #$00
lda (sp),y
sta BankNum
ldy #$01
;ldx #$00
lda (sp),y
sta RamAddr
ldy #$00
;ldx #$00
lda (sp),y
sta RamVal

; if Bank #1, jump to lwrextram
  lda BankNum
  bne lwrextram

; switch to Bank 0
  jsr Switch2Bank0

; A = address
; X = value
; write RAM
  lda RamAddr
  ldx RamVal
  jsr WrRTC
; exit
  jsr incsp3
  rts

; Write RAM in Bank 1
lwrextram:

  jsr Switch2Bank1
; load RAM addr. into extended ram address register
  ldx RamAddr
  lda #ExtRamAddr
  jsr WrRTC
; load RAM value into extended RAM port
  ldx RamVal
  lda #ExtRamPort
  jsr WrRTC

; switch to Bank 0
  jsr Switch2Bank0

; exit
  jsr incsp3
  rts

.endproc

.segment "CODE"

; read value from non-volatile RAM
; unsigned char __fastcall__ ds1685_readram (unsigned char bank,
;                                    unsigned char addr);

.proc _ds1685_readram: near

.segment "CODE"
; get parameters, put them in temp. buffer
jsr pusha
ldy #$01
;ldx #$00
lda (sp),y
sta BankNum
ldy #$00
;ldx #$00
lda (sp),y
sta RamAddr

; if Bank #1, jump to lwrextram
  lda BankNum
  bne lrdextram

; switch to Bank 0
  jsr Switch2Bank0

; A = address
; read RAM
  lda RamAddr
  jsr RdRTC
  sta Temp
; exit
  lda Temp
  ldx #00
  jsr incsp2
  rts

; read RAM from Bank 1
lrdextram:

  jsr Switch2Bank1
; load RAM addr. into extended ram address register
  ldx RamAddr
  lda #ExtRamAddr
  jsr WrRTC
; load RAM value into extended RAM port
  lda #ExtRamPort
  jsr RdRTC
  sta Temp

; switch to Bank 0
  jsr Switch2Bank0

; exit
  lda Temp
  ldx #00
  jsr incsp2
  rts

.endproc

.segment "CODE"

; helper procedures

;-------------------------------------------------------------------------------
; Write DS1685 address (Acc).
;-------------------------------------------------------------------------------

WrRTCAddr:
sta DSCALADDR
rts

;-------------------------------------------------------------------------------
; Write DS1685 data (Acc).
;-------------------------------------------------------------------------------

WrRTCData:
sta DSCALDATA
rts

;-------------------------------------------------------------------------------
; Read DS1685 data (-> Acc).
;-------------------------------------------------------------------------------

RdRTCData:
lda DSCALDATA
rts

;-------------------------------------------------------------------------------
; Write DS1685 Acc = Addr, X = Data
;-------------------------------------------------------------------------------

WrRTC:
jsr WrRTCAddr
txa
jsr WrRTCData
rts

;-------------------------------------------------------------------------------
; Read DS1685 Acc = Addr -> A = Data
;-------------------------------------------------------------------------------

RdRTC:
jsr WrRTCAddr
jsr RdRTCData
rts

;-------------------------------------------------------------------------------
; Transfer A to return buffer at index Y.
;-------------------------------------------------------------------------------

Tfer2RetBuf:

pha
tya
pha
  ldy     #$01 ; transfer to return buffer
  jsr     ldaxysp
  jsr     pushax
  ldx     #$00
pla
tay
pla
  jsr     staspidx
rts

;-------------------------------------------------------------------------------
; Load to A from arguments buffer/stack at index Y.
;-------------------------------------------------------------------------------

GetParFromSpIdx:

tya
pha
  ldy   #$01 ; get buffer
  jsr   ldaxysp
sta Temp
pla
tay
lda Temp
  jsr   ldauidx
rts

;-------------------------------------------------------------------------------
; Swicth to RTC registers in bank 0.
;-------------------------------------------------------------------------------

Switch2Bank0:

  lda #$0a        ; get register A
jsr RdRTC
and #DSC_REGA_BANK0  ; switch to bank 0
tax
lda #$0a        ; write register A
jsr WrRTC
  rts

;-------------------------------------------------------------------------------
; Swicth to RTC registers in bank 0.
;-------------------------------------------------------------------------------

Switch2Bank1:

lda #$0a ; get reg. A
jsr RdRTC
ora #DSC_REGA_BANK1 ; switch to bank 1
tax
lda #$0a      ; write reg. A
jsr WrRTC
  rts


;------------------------------ END OF FILE -------------------------------------

Presented below is the computer now in full glory with PropTermMK device, PC keyboard and small VGA display.

I also added few screenshots of the PropTermMK features and NV RAM access functions in action.

This is all I have time for today. I know I promised to finally publish all firmware code and blueprints to GitHub, but I need to clean up the code some more before I do that and some pressing home improvement projects are now pulling me away from this one.

Thank you for visiting my blog.

MK 6/19/2017