MC68711E20CFNE3 Datasheet, PDF (224/242 Pages) –

Listing 3. MC68HC711E9 Bootloader ROM
107
* This routine uses 2 bytes of stack space
108
* Routine does not return. Reset to exit.
109
****************************************************
110 BF13
PRGROUT EQU *
111 BF13 3C
PSHX
Save program delay constant
112 BF14 CE1000
LDX #$1000
Point to internal registers
113 BF17
114
* Send $FF to indicate ready for program data
115
116 BF17 1F2E80FC
BRCLR SCSR,X $80 * Wait for TDRE
117 BF1B 86FF
LDAA #$FF
118 BF1D A72F
STAA SCDAT,X
119
120 BF1F
WAIT1 EQU *
121 BF1F 1F2E20FC
BRCLR SCSR,X $20 * Wait for RDRF
122 BF23 E62F
LDAB SCDAT,X
Get received byte
123 BF25 18E100
CMPB $0,Y
See if already programmed
124 BF28 271D
BEQ DONEIT
If so, skip prog cycle
125 BF2A 8620
LDAA #ELAT
Put EPROM in prog mode
126 BF2C A73B
STAA PPROG,X
127 BF2E 18E700
STAB 0,Y
Write the data
128 BF31 8621
LDAA #ELAT+EPGM
129 BF33 A73B
STAA PPROG,X
Turn on prog voltage
130 BF35 32
PULA
Pull delay constant
131 BF36 33
PULB
into D-reg
132 BF37 37
PSHB
But also keep delay
133 BF38 36
PSHA
keep delay on stack
134 BF39 E30E
ADDD TCNT,X
Delay const + present TCNT
135 BF3B ED16
STD TOC1,X
Schedule OC1 (2ms delay)
136 BF3D 8680
LDAA #OC1F
137 BF3F A723
STAA TFLG1,X
Clear any previous flag
138
139 BF41 1F2380FC
BRCLR TFLG1,X OC1F * Wait for delay to expire
140 BF45 6F3B
CLR PPROG,X
Turn off prog voltage
141
*
142 BF47
DONEIT EQU *
143 BF47 1F2E80FC
BRCLR SCSR,X $80 * Wait for TDRE
144 BF4B 18A600
LDAA $0,Y
Read from EPROM and...
145 BF4E A72F
STAA SCDAT,X
Xmit for verify
146 BF50 1808
INY
Point at next location
147 BF52 20CB
BRA WAIT1
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148
* Loops indefinitely as long as more data sent.
149
150
****************************************************
151
* Main bootloader starts here
152
****************************************************
153
* RESET vector points to here
154
155 BF54
BEGIN EQU *
156 BF54 8E01FF
LDS #RAMEND
Initialize stack pntr
157 BF57 CE1000
LDX #$1000
Point at internal regs
158 BF5A 1C2820
BSET SPCR,X $20
Select port D wire-OR mode
159 BF5D CCA20C
LDD #$A20C
BAUD in A, SCCR2 in B
160 BF60 A72B
STAA BAUD,X
SCPx = ÷4, SCRx = ÷4
161
* Writing 1 to MSB of BAUD resets count chain
M68HC11 Bootstrap Mode, Rev. 1.1
224
Freescale Semiconductor