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AN2635 Datasheet(PDF) 9 Page - Freescale Semiconductor, Inc |
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AN2635 Datasheet(HTML) 9 Page - Freescale Semiconductor, Inc |
9 / 36 page How to Use the Routines On-Chip FLASH Programming Routines, Rev. 4 Freescale Semiconductor 9 Example 2: Sending a Byte Serially Example 2 shows how to send a byte ($55) serially on PTA0: PutByte equ $0381 ;LB8 PutByte jump address bclr 0,DDRA ;Configure port A bit 0 as an input bclr 0,PTA ;Initialize data bit to zero PTA0=0 lda #$55 ;Load sent data $55 to A jsr PutByte ;Call PutByte routine RDVRRNG When using the RDVRRNG routine, the user must select one of the following function options: • Send-out option — Used to read a range of FLASH locations and to send the read data to a host through PTA0 by using the PutByte routine. • Verify option — Used to read a range of FLASH locations and to verify the read data against the DATA array. Send-Out Option If the accumulator (A) is initialized with $00 at the routine entry, the read data will be sent out serially through PTA0. The communication baud rate is the same as the baud rate described in the PutByte routine. When this option is selected, the PTA0 must be pulled up and configured as an input and the PTA0 data bit must be initialized to 0. Verify Option If A is initialized with a non-zero value, the read data is verified against the DATA array for each byte of FLASH and the DATA array is replaced by the data read from FLASH. If the data does not match the corresponding value, the data read from FLASH can be confirmed in the DATA array. All data in the DATA array must be in the zero page, but a range can be beyond a row size or a page size. Carry (C) Bit and Checksum The first and last addresses of the range to be read and/or verified are specified as parameters in registers H:X and LADDR, respectively. In the verify option, the carry (C) bit of the condition code register (CCR) is set if the data in the specified range is verified successfully against the data in the DATA array. However when the send-out option is selected, the status of the C bit is meaningless because this function does not include the verify operation. Both options calculate a checksum on data read in the range. This checksum, which is the LSB of the sum of all bytes in the entire data collection, is stored in A upon return from the function. Interrupts are not masked. The COP is serviced in RDVRRNG. The first COP is serviced at 23 bus cycles after this routine is called in the user software. However, the COP timeout might still occur in the send-out option if the COP is configured for a short timeout period. |
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