Здравствуйте, в файле в исходниках от openmsp430 - omsp_gpio.v есть следующее:
// Register base address (must be aligned to decoder bit width)
parameter [14:0] BASE_ADDR = 15'h0000;
// Decoder bit width (defines how many bits are considered for address decoding)
parameter DEC_WD = 6;
// Register addresses offset
parameter [DEC_WD-1:0] P1IN = 'h20, // Port 1
P1OUT = 'h21,
P1DIR = 'h22,
P1IFG = 'h23,
P1IES = 'h24,
P1IE = 'h25,
P1SEL = 'h26,
P2IN = 'h28, // Port 2
P2OUT = 'h29,
P2DIR = 'h2A,
P2IFG = 'h2B,
P2IES = 'h2C,
P2IE = 'h2D,
P2SEL = 'h2E,
P3IN = 'h18, // Port 3
P3OUT = 'h19,
P3DIR = 'h1A,
P3SEL = 'h1B,
P4IN = 'h1C, // Port 4
P4OUT = 'h1D,
P4DIR = 'h1E,
P4SEL = 'h1F,
P5IN = 'h30, // Port 5
P5OUT = 'h31,
P5DIR = 'h32,
P5SEL = 'h33,
P6IN = 'h34, // Port 6
P6OUT = 'h35,
P6DIR = 'h36,
P6SEL = 'h37;
// Register one-hot decoder utilities
parameter DEC_SZ = (1 << DEC_WD);
parameter [DEC_SZ-1:0] BASE_REG = {{DEC_SZ-1{1'b0}}, 1'b1};
// Register one-hot decoder
parameter [DEC_SZ-1:0] P1IN_D = (BASE_REG << P1IN), // Port 1
P1OUT_D = (BASE_REG << P1OUT),
P1DIR_D = (BASE_REG << P1DIR),
P1IFG_D = (BASE_REG << P1IFG),
P1IES_D = (BASE_REG << P1IES),
P1IE_D = (BASE_REG << P1IE),
P1SEL_D = (BASE_REG << P1SEL),
P2IN_D = (BASE_REG << P2IN), // Port 2
P2OUT_D = (BASE_REG << P2OUT),
P2DIR_D = (BASE_REG << P2DIR),
P2IFG_D = (BASE_REG << P2IFG),
P2IES_D = (BASE_REG << P2IES),
P2IE_D = (BASE_REG << P2IE),
P2SEL_D = (BASE_REG << P2SEL),
P3IN_D = (BASE_REG << P3IN), // Port 3
P3OUT_D = (BASE_REG << P3OUT),
P3DIR_D = (BASE_REG << P3DIR),
P3SEL_D = (BASE_REG << P3SEL),
P4IN_D = (BASE_REG << P4IN), // Port 4
P4OUT_D = (BASE_REG << P4OUT),
P4DIR_D = (BASE_REG << P4DIR),
P4SEL_D = (BASE_REG << P4SEL),
P5IN_D = (BASE_REG << P5IN), // Port 5
P5OUT_D = (BASE_REG << P5OUT),
P5DIR_D = (BASE_REG << P5DIR),
P5SEL_D = (BASE_REG << P5SEL),
P6IN_D = (BASE_REG << P6IN), // Port 6
P6OUT_D = (BASE_REG << P6OUT),
P6DIR_D = (BASE_REG << P6DIR),
P6SEL_D = (BASE_REG << P6SEL);
т.е. 6-битной шине P1IN_D присваивается BASE_REG смещенный влево на 32:
parameter [DEC_SZ-1:0] P1IN_D = (BASE_REG << P1IN)
Помогите разобраться как такое может быть в чем смысл такого смещения?
