20-668-0003 Rabbit Semiconductor, 20-668-0003 Datasheet - Page 118

• Manufacturer Part Number: 20-668-0003
• Description: IC CPU RABBIT2000 30MHZ 100PQFP
• Manufacturer: Rabbit Semiconductor

Specifications of 20-668-0003

• Processor Type: Rabbit 2000 8-Bit
• Speed: 30MHz
• Voltage: 2.7V, 3V, 3.3V, 5V
• Mounting Type: Surface Mount
• Package / Case: 100-MQFP, 100-PQFP
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 30 MHz
• Operating Supply Voltage: 0 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Number Of Programmable I/os: 40
• Number Of Timers: 8 & 10 bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 20-668-0003; 316-1062

11.1 Timer A
Timer A consists of five separate countdown timers—A1 and A4–A7—as shown in
Figure 11-1.
Timers A1 and A4–A7 are 8-bit countdown registers as shown in Figure 11-2. The reload
register can contain any number in the range from 0 to 255. The counter divides by (n+1).
For example, if the reload register contains 127, then 128 pulses enter on the left before a
pulse exits on the right. If the reload register contains zero, then each pulse on the left
results in a pulse on the right, that is, there is division by one.
The timer systems are driven by the peripheral clock divided by two. This clock is always
the same as the processor clock, or it is faster than the processor clock by a factor of eight.
The output pulses are always one clock long. Clocking of the counters takes place on the
negative edge of this pulse. When the counter reaches zero, the reload register is loaded on
the next input pulse instead of a count being performed. The reload registers may be
reloaded at any time since the peripheral clock is synchronous with the processor clock.
Timers A4, A5, A6 and A7 always provide the baud clock for serial ports A, B, C and D
respectively. Except for very low baud rates, clock A1 does not need to be used to prescale
the input clock for timers A4–A7. For example, if the system clock is 11.0592 MHz, and if
the timer A4 divides by 144, an asynchronous baud rate of 2400 bps can be achieved in one
step. The clock input to the serial port must be 16 times the baud rate for asynchronous
mode and 8 times the baud rate for synchronous mode. The maximum asynchronous baud
rate with a 11.0592 MHz clock would be (11,059,200/(2*16) = 345,600.
Each of the five countdown registers in timer A can cause an interrupt. There is one inter-
rupt vector for timer A and a common interrupt priority. A common status register
(TACSR) has a bit for each timer that indicates if the output pulse for that timer has taken
112
Clock in
Input Clock
Count value
8-bit reload register
8-bit down counter
Figure 11-2. Reload Register Operation
2
Output pulse
2
1
1
load
0
Rabbit 2000 Microprocessor User’s Manual
0
pulse on zero count out
N
N - 1