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CHAPTER 7 REGISTERS
340
(19) Frequency Justification count register (FJCT)
7
0
Address
Default
R/W
FJCT
12H
00H
R
FJC = 1
FJC = 0
15
12 11
8
7
0
FJCNTR
0
0
0
0
The SMP bit is set to 1
11
8
7
0
FJ counter
This is a window register that is used to read the value held in the 12-bit
FJCNTR
register by reading eight
bits and four bits, two times. First, the low-order eight bits of the register (
FJCNTR[7:0]
) are read, after
which the high-order four bits (
FJCNTR[11:8]
) are read. Whether the high- or low-order bits are read is
indicated by the setting of the
FJC
bit of the
PCPR1
register (address: 19H). By default the
FJC
bit of the
PCPR1
register is set to 0. This is changed automatically (from 0 to 1 to 0, etc.) every time the
FJCT
register is read.
FJCNTR
is a load register that is used to sample (store) the value of the
FJ counter
. By setting the
SMP
bit of the
PCSR
register (address: 1BH) to 1, the value of the
FJ counter
is stored into the
FJCNTR
register. This value indicates the number of times Frequency Justification has been applied since the
contents of the
FJ counter
were last sampled. The value stored into the
FJCNTR
register is held until the
FJ counter
is next sampled.
Sampling the contents of the
FJ counter
causes the counter to be cleared to 0. The counter is also
cleared to 0 when the
FJC
bit of the
PCIR1
register (address: 1CH) is set to 1.
When the value of the counter is all F, the
FJC
bit of the
PCOCR1
register (address: 20H) is set to 1 to
indicate a counter overflow being detected. Also, the
PCO
bit of the
PICR
register (address: 06H) is set to
1, thus causing an interrupt. After the occurrence of an overflow, the
FJ counter
again starts to count up
from 0.