
PERIPHERAL INTERFACING – III 11.31
signal, de-asserts its HRQ pin, lowers the AEN signal and releases the system bus, so that the
process can resume its normal operation.
11.6.4 | Initialization and Programming the 8237
Continuing with the idea of programming the 8237 chip, let us see the registers it has for com-
mand, status and modes. Since we have designed the logic of CS as in Fig 11.22, the addresses
of these registers are as in Table 11.4.
Command/Status Register e command register is the register used for controlling the
operation of the DMA chip. For that, the register must be written to. e same register is used
as a status register ...