4 bit 7 segment display with two 74HC595

[richard]

Could you point to an example of that?

me too
I have never had to do that and can find no mention of that short coming anywhere


anyways here is my take on the 7 seg display
if you have a chip with mssp why waste time and code space when the hardware can do it for you

I cheated a bit and did it in asm for speed and size gains
no nasty pauses , all gone
my displays are common anode so the data is inverted see comments

'****************************************************************
'*  Name    : 4 bit 7 segment display                           *
'*  Author  : RICHARD                                           *
'*  Notice  :                                                   *
'*          :                                                   *
'*  Date    : 18. 2. 2018                                       *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*  MCU     : PIC 16F1825 @32MHZ                                *
'****************************************************************
#CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_OFF & _LVP_OFF
#ENDCONFIG

 goto overasm
 asm
timer1  = TMR1L 
 
seg_val       
    addwf   PCL, F                  
    retlw  0xc0;0B11000000     0  
    retlw  0xf9;0B11111001     1     
    retlw  0xa4;0B10100100     2
    retlw  0xb0;0B10110000     3
    retlw  0x99;0B10011001     4
    retlw  0x92;0B10010010     5                     
    retlw  0x82;0B10000010     6
    retlw  0xf8;0B11111000     7
    retlw  0x80;0B10000000     8  
    retlw  0x90;0B10010000     9
 endasm

 overasm:
DEFINE OSC 32            ; Use internal clock 
ANSELC=0
SSP1CON1=$22  
SSP1STAT=$40
OSCCON=$f0

INCLUDE "DT_INTS-14.bas" ; Base Interrupt System

TRISC = %11101010
LPIN var portc.4         ; Latch
DPIN var portc.2         ; Data  SDO
CPIN var portc.0         ; Clock SCK
segment var byte
value var word
d_index var byte
buff var byte[5]
tmp var byte             
d_pointer      var byte  
timer1 var word ext
timer1_reload con    1543      ;8mS
ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
    INT_Handler TMR1_INT, _DISP, ASM, yes
  endm
  INT_CREATE ; Creates the interrupt processor
ENDASM
@ INT_ENABLE TMR1_INT ; enable Timer 1 interrupts
T1CON = $1
d_index=0
;---[simple counter 0 - to 9999]------------------------------------------------ 
Main:
for value = 0 to 9999
arraywrite buff ,[dec4 value]
pause 100
next value
value = 0
GOTO Main
;---[TMR1 - interrupt handler]--------------------------------------------------
DISP:
asm
    MOVE?CT 0, T1CON, TMR1ON ; 1 stop timer
    MOVLW LOW(_timer1_reload) ; 1 Add TimerReload to the 
    ADDWF TMR1L,F ; 1 value in Timer1
    BTFSC STATUS,C ; 1/2
    INCF TMR1H,F ; 1
    MOVLW HIGH(_timer1_reload) ; 1
    ADDWF TMR1H,F ; 1
    MOVE?CT 1, T1CON, TMR1ON ; 1 start timer
    MOVE?CB  high _buff, FSR0H         ;load highbyte 
    MOVE?CB  low  _buff, FSR0L         ;load low byte
    MOVE?BA  _d_index  
    ADDWF  FSR0L,F
    MOVLW 0X30
    SUBWF INDF0,W
    L?CALL seg_val
    MOVE?AB _segment
    MOVE?BB  _d_index ,_tmp
    BANKSEL   _tmp
    MOVLW 1
    ADDWF  _tmp,F
    BANKSEL   _d_pointer
    CLRF _d_pointer
    BSF STATUS ,C
N_BIT 
    BANKSEL   _d_pointer
    RLF    _d_pointer,F
    BCF STATUS ,C
    BANKSEL   _tmp
    DECFSZ  _tmp,F
    GOTO N_BIT 
    MOVLW 1
    BANKSEL  _d_index
    ADDWF  _d_index,F
    MOVLW 3 
    ANDWF  _d_index,F
    BANKSEL  LATC
    BCF LATC ,4
    BANKSEL PIR1
    BCF     PIR1,3 
    BANKSEL  _segment
    COMF    _segment,W  ;COMMENT USED TO INVERT DATA FOR COMMON ANODE DISPLAY
    BANKSEL SSP1BUF
    movwf   SSP1BUF
    BANKSEL PIR1
    BTFSs   PIR1,3
    GOTO    $-1
    BANKSEL  _d_pointer
    COMF    _d_pointer,W ; ;COMMENT USED FOR COMMON ANODE DISPLAY
    BANKSEL PIR1
    BCF     PIR1,3 
    BANKSEL SSP1BUF
    movwf   SSP1BUF
    BANKSEL PIR1
    BTFSs   PIR1,3
    GOTO    $-1
    BANKSEL  LATC
    BSF LATC ,4
    BANKSEL 0
    INT_RETURN
endasm