MB87P2020 Datasheet, PDF (53/356 Pages) Fujitsu Component Limited. – Colour LCD/CRT/TV Controller

User Logic Bus
Beside the chip select signal configuration the 16 Bit mode has to be selected for the address space of
GDC(s) within MCU (see MB91360 series hardware manual) and with MODE[2] pin (1: 32Bit mode;
0: 16Bit mode) at the display controller. All data transfer is done at MSB side of data bus (Pins:
ULB_D[31:16]). For write accesses does this mean that the bus signals ULB_WRX[2:3] are not used
and should be set to ’1’ in 16Bit mode. Table 1-9 gives an overview on used parts of data bus and used con-
trol signals.
Table 1-9: Signal connection for data modes
Signal
Data bus
Write control signals
Read control signals
Data mode
32 Bit data mode
(MODE[2]=1)
16 Bit data mode
(MODE[2]=0)
ULB_D[31:0]
ULB_D[31:16]
ULB_WRX[3:0]
ULB_WRX[1:0]
set ULB_WRX[3:2] to ’1’
(pull up)
ULB_RDX
ULB_RDX
In 16Bit mode display controller address space (register and SDRAM space) is accessible as in 32Bit mode.
All bus access types described in chapter 1.4.4 can be used transparently.
For word write accesses a MB91xxxx MCU splits the word access into two half word accesses with con-
secutive addresses (increment two). Since the display controller is able to handle half word and byte access-
es (see chapter 1.4.4) 16Bit mode can be supported.
ULB contains a 16Bit to 32Bit converter that is responsible for adapting the 16Bit bus access to internal
32Bit bus structure. For the special case of FIFO write access, where only word access is allowed not only
in 16Bit data mode, a special circuit was included which collects data for FIFO write access.
For read accesses ULB contains an additional converter which is responsible for converting the internal
32Bit bus structure to external 16Bit bus structure. For reading from output FIFO a special circuit is in
charge of reading only once from FIFO and store the value for second read.
1.5 Command decoding and execution
1.5.1 Command and data interface to MCU
The display controller command interface to MCU consists of the following main parts:
• Command register where command instruction and command coded parameters can be written and read
• Input- and output FIFO for data exchange between MCU and display controller
• Command dependent flags set by command controller
• Debug register (read only) in order to watch command controller behaviour
Writing to command register has to be synchronised with command execution within display controller. In
chapter 1.5.3 the structure and function of ULB’s command decoder will be explained in detail. From pro-
grammers’ point of view a flag (FLNOM_CWEN) shows when command controller is able to receive a new
command. An application should poll FLNOM_CWEN flag before writing a new command or if interrupt
controlled flow is implemented it should write commands only after FLNOM_CWEN causes an interrupt.
If the display controller ’Application Programming Interface (API)’ is used, flag polling is done automati-
cally before writing a new command. Figure 1-6 shows the draw line command within API as an example.
word GDC_CMD_DwLn(dword line_col) {
while (!G0FLNOM_CWEN); /* Wait until Command Write Enable flag is set */
1. This MCU should have the same bus interface as MB91xxxx or it has to be adapted with help of glue logic.
Functional description
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