1996 Jun 27 101
Philips Semiconductors Product specification
8-bit microcontroller with on-chip CAN P8xC592
00A0 107 ; determine the destination address in data-memory for the
00A1 108 ; message's Data-Field
54E0 109 ANL A, #ID2_0_MASK ; use ID.2 ... ID.0 only
C4 110 SWAP A
03 111 RR A ; A = 4*ID.2 + 2*ID.1 + ID.0
112 ; this value is used as an index for an array of 8 bytes
113 ; containing the destination-addresses for the 8 different
114 ; messages. Note, that the #RX_ARRAY_OFFSET is due to the
00A2 115 ; program counter-relative access to the array.
2415 116 ADD A, #RX_ARRAY_START − RX_ARRAY_OFFSET
83 117 MOVC A, @A + PC
118 RX_ARRAY_OFFSET:
119
00A5 120 ; if a message passes the acceptance-filter of the CAN
00A7 121 ; Controller, but the CPU doesn't need it, the array
122 ; entry's value may be set to zero indicating this.
123 ; The following <jz> instruction cares for this.
6007 124 JZ CAN_RX_READY
00A9 125
00AB 126 ; now copy the Data-Field (only) from CAN- to CPU memory
00AD 127 ; with the aid of the DMA-logic. Note, that a TX-DMA is
128 ; performed when writing 8AH (DMA + address 10) into CANADR
129 ; and a RX-DMA is performed when writing 94H (DMA + address 20)
130 ; ... 9DH (DMA + address 29) into CANADR. Here address 22 is
131 ; used to copy just the Data-Field.
F5D8 132 MOV CANSTA, A ; data-memory address
75DB96 133 MOV CANADR, #CAN_RX_DMA ; starts RX-DMA at address 22
134
00AE 135 ; the DMA-transfer is done in at maximum 2 instruction cycles.
00AF 136 ; During the transfer, neither the data-memory (RAM) nor one
137 ; of the SFRs CANADR, CANDAT, CANCON and
00B0 138 ; CANSTA may be accessed by the CPU.
139 ; For simplicity, two NOPs are used here.
00 140 NOP
00 141 NOP
00A0 142
LOC OBJ LINE SOURCE
