156
Rabbit 3000 Microprocessor
11.2 Timer B
Figure 11-1 shows a block diagram of Timer B. The Timer B counter can be driven
directly by perclk/2, by that clock divided by 8, or by the output of Timer A1. Timer B has
a continuously running 10-bit counter. The counter is compared against two match regis-
ters, the B1 match register and the B2 match register. When the counter transitions to a
value equal to a match register, an internal pulse with a length of 1 peripheral clock is gen-
erated. The match pulse can be used to cause interrupts and/or clock the output registers of
Parallel Ports D and E.
The match registers are loaded from the match preload registers that are written to by an
I/O instruction. The data byte in the match preload register is advanced to the next match
register when the match pulse is generated.
Every time a match condition occurs, the processor sets an internal bit that marks the match
value in TBLxR as invalid. Reading TBCSR clears the interrupt condition. TBLxR must be
reloaded to re-enable the interrupt. TBMxR does
not
need to be reloaded every time.
If both match registers need to be changed, the most significant byte needs to be changed
first.
The I/O registers for Timer B are listed in Table 11-6.
Table 11-6. Timer B Registers
Register Name
Mnemonic
I/O
address
R/W
Reset
Timer B Control/Status Register
TBCSR
0xB0
R/W
xxxxx000
Timer B Control Register
TBCR
0xB1
W
xxxx0000
Timer B MSB 1 Register
TBM1R
0xB2
W
xxxxxxxx
Timer B LSB 1 Register
TBL1R
0xB3
W
xxxxxxxx
Timer B MSB 2 Register
TBM2R
0xB4
W
xxxxxxxx
Timer B LSB 2 Register
TBL2R
0xB5
W
xxxxxxxx
Timer B Count MSB Register
TBCMR
0xBE
R
xxxxxxxx
Timer B Count LSB Register
TBCLR
0xBF
R
xxxxxxxx
Содержание Rabbit 2000
Страница 2: ...Rabbit 3000 Microprocessor User s Manual 019 0108 040731 O ...
Страница 9: ...Rabbit 3000 Microprocessor ...
Страница 29: ...20 Rabbit 3000 Microprocessor ...
Страница 64: ...User s Manual 55 5 PIN ASSIGNMENTS AND FUNCTIONS ...
Страница 79: ...70 Rabbit 3000 Microprocessor ...
Страница 80: ...User s Manual 71 6 RABBIT INTERNAL I O REGISTERS ...
Страница 123: ...114 Rabbit 3000 Microprocessor ...
Страница 137: ...128 Rabbit 3000 Microprocessor ...
Страница 157: ...148 Rabbit 3000 Microprocessor ...
Страница 207: ...198 Rabbit 3000 Microprocessor ...
Страница 249: ...240 Rabbit 3000 Microprocessor ...
Страница 255: ...246 Rabbit 3000 Microprocessor ...
Страница 277: ...268 Rabbit 3000 Microprocessor ...
Страница 343: ...334 Rabbit 3000 Microprocessor ...
Страница 345: ......