Carrier Generator - Epson S1C17704 Technical Manual

21.3 Carrier Generator

The REMC module contains a carrier generator that generates a transmit carrier signal according to the clock, H
carrier length, and L carrier length set with software.
A prescaler output clock is used to generate the carrier signal. Use the CGCLK[3:0] bits (D[7:4]/REMC_PSC
register) to select one from the 15 clocks, PCLK divided by 1 to PCLK divided by 16K, generated by the prescaler.
∗ CGCLK[3:0]: Carrier Generator Clock Select Bits in the REMC Prescaler Clock Select (REMC_PSC) Register
(D[7:4]/0x5341)
CGCLK[3:0]
0xf
0xe
0xd
0xc
0xb
0xa
0x9
0x8
For controlling the prescaler, see Chapter 9, "Prescaler (PSC)."
Note: Before the REMC module can be used, the prescaler must be run.
The lengths of H period and L period of the carrier signal can be set using REMCH[5:0] (D[5:0]/REMC_CARH
register) and REMCL[5:0] (D[5:0]/REMC_CARL register). The H/L period lengths should be set as the number of
clock (selected as above) cycles +1.
∗ REMCH[5:0]: H Carrier Length Setup Bits in the REMC H Carrier Length Setup (REMC_CARH) Register
(D[5:0]/0x5342)
∗ REMCL[5:0]: L Carrier Length Setup Bits in the REMC L Carrier Length Setup (REMC_CARL) Register
(D[5:0]/0x5343)
The H and L carrier lengths are calculated by the expressions below.
REMCH + 1
H carrier length = —————— [s]
REMCL + 1
L carrier length = —————— [s]
REMCH: H carrier length register data
REMCL: L carrier length register data
clk_in: Prescaler output clock frequency
The carrier signal is generated according to these settings as shown in Figure 21.3.1.
Example: CGCLK[3:0] = 0x2 (PCLK•1/4), REMCH[5:0] = 2, REMCL[5:0] = 1
PCLK
PSC output clock
Count
Carrier
S1C17704 TECHNICAL MANUAL
Table 21.3.1 Selecting a Clock for Carrier Generator
Prescaler output clock
Reserved
PCLK•1/16384
PCLK•1/8192
PCLK•1/4096
PCLK•1/2048
PCLK•1/1024
PCLK•1/512
PCLK•1/256
clk_in
clk_in
0 1
H carrier length
Figure 21.3.1 Carrier Signal Generation
21 REMOTE CONTROLLER (REMC)
CGCLK[3:0]
0x7
0x6
0x5
0x4
0x3
0x2
0x1
0x0
2 0
L carrier length
EPSON
Prescaler output clock
PCLK•1/128
PCLK•1/64
PCLK•1/32
PCLK•1/16
PCLK•1/8
PCLK•1/4
PCLK•1/2
PCLK•1/1
(Default: 0x0)
1 0
21-3