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CS4237B Datasheet(PDF) 24 Page - Cirrus Logic |
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CS4237B Datasheet(HTML) 24 Page - Cirrus Logic |
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24 / 114 page  Bytes 19 through 21 map the interrupt number to the actual interrupt pins A - F. As shown in the table, the byte 20 default is 0xB9; therefore, IRQC, which is the lower nibble, maps to the ISA interrupt 9. Likewise IRQD, which is the upper nibble, maps to the ISA interrupt 11 (0Bh). Bytes 22 and 23 map the DMA channel number to the actual DMA pins A-C. As shown in the table, the byte 22 default is 0x10; therefore, DRQA/DACKA is the lower nibble which maps to the ISA DMA chan nel 0. Like wise DRQB/DACKB is the upper nibble which maps to the ISA DMA channel 1. Hostload Procedure This procedure is provided for backwards com- patibility with the CS4236. Since the E 2PROM allows all resource and firmware patch data to be loaded at power-up, this procedure is typically not used. To download PnP resource data from the host to the part’s internal RAM, use the fol- lowing sequence: 1. Configure Control I/O base address, CTRLbase, by one of two methods: regular PnP cycle or Crystal Key method. a. The host can use the regular PnP cycle to program the CTRLbase, and then place the chip in the wait_for_key_state b. If the Crystal Key method is used: First, send the 32-byte Crystal key to I/O address 0279h. (The Crystal Key only supports one Crystal part per system.) Second, configure logical device 2 base address, CTRLbase, by writing to I/O 0279h (15h, 02h, 47h, xxh, xxh, 33h, 01h, 79h). Note: The two xxh represent the base_ad- d re ss_h i gh an d b ase_a ddre ss_l ow respectively. The default is: 01h, 20h. 2. Write 57h (Jump to ROM) command to CTRLbase+5. 3. Download the PnP resource data. a. Send download command by writing AAh to CTRLbase+5. b. Send starting download address (4000h) by writing low byte (00h) first, and then high byte (40h) to CTRLbase+5. c. Send the Hardware Configuration and re- so u rc e d a ta in su cce ssiv e by tes to CTRLbase+5. This includes the Hardware Configuration and the PnP resource data. The PnP resource format is described in the PnP Data section. The resource header should not contain the first four bytes which are only used for E 2PROM loads. 4 . E nd do wnl oad b y writi ng 00 h to CTRLbase+6. 5. If any of the Hardware Configuration Data (first 19 bytes) has changed, 5Ah must be written to CTRLbase+5 to force the part to internally update this information. The new PnP data is loaded and the part is ready for the next PnP cycle. External E 2PROM The Plug and Play specification defines 32 bits of the 72-bit Serial Identifier as being a user de- fined serial number. The E 2PROM is used to change the user section of the identifier, store default resource data for PnP, Hardware Con- figuration data specific to the Crystal part, and firmware patches to upgrade the core processor functionality. DS213PP4 CS4237B 24 |
Similar Part No. - CS4237B |
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Similar Description - CS4237B |
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