Manual
37
AT86RF401
1424D–RKE–09/02
Bit Timer Register Descriptions
Bit Timer Count Register – BTCNT
• Bit [7:0]
Lowest 8 bits of
countval
. When combined with bits [7:6] of the BTCR register,
countval
determines a counter value that sets the width of a mark or a space that is sent to the
transmitter. The width of the mark or space is:
P
XX
=P
AVR
*
(countval
+1)
where
P
XX
is the period of the mark or space, and
P
AVR
is the period of the AVR clock
that is determined by the ACS bits of the AVR configuration register, AVR_CONFIG.
Bit Timer Control Register – BTCR
• Bit[7:6]
Count_val[9:8]. MSB of BTCNT counter value bits.
• Bits[5:4]
Bit Timer Mode.
• Bit[3]: Interrupts Enabled
If this bit is set, the Flag2 and Flag0 will generate their respective interrupts when they
are set. Flag0 interrupt vector is located at 0 x 04. Flag2 interrupt vector is located at
0 x 02. Typically, a JMP instruction resides at these vector locations to pass control to
an interrupt handler. For Flag0 only, slightly faster execution can be achieved if the JMP
instruction is eliminated, and the interrupt service routine is located beginning at 0 x 04.
Bit 76543210
$20 C7 C6 C5 C4 C3 C2 C1 C0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 00000000
Bit 76543210
$21 C9 C8 M1 M0 IE F2 DATA F0
Read/Write R/W R/W R/W R/W R/W R R/W R
Initial Value 00000000
Mode[1:0] Bit Timer Function
00 Bit Timer Disabled
01 Transmit Mode, Transmitter Not Keyed
10 Receive Mode
11 Transmit Mode, Transmitter Keyed