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OCPRF100 MP Server System Technical Product Specification
Revision 1.0
101
8.6.1.3.3 Drive Present Status Region (0xFA00 – 0xFAFF)
The absence or presence of each drive is detected by the state of pin 44 on that drive’s SCA con-
nector. A drive that is present will have its corresponding bit set to one in this register. Bits 7:6 in
this register indicate the revision of the PLD code that is installed.
SCSI Target Access Region (0xFB00 – 0xFBFF)
The Symbios 53C80 SCSI target appears to the controller as a set of eight registers at sequential
addresses. For details, refer to the Symbios SYM53C80E/S Data Manual.
8.6.1.3.4 SCSI DACK Access Region (0xFC00 – 0xFCFF)
When the SCSI target is in DMA mode, data bytes may be read from or written to the 53C80S by
reading or writing the DACK access region. This asserts the DACK_L input of the 53C80S
instead of the CS_L input.
8.6.2 I/O Ports
80C652 architecture provides four memory-mapped I/O ports:
• Port #0 (P0).
• Port #1 (P1).
• Port #2 (P2).
• Port #3 (P3).
8.6.2.1 P0
Since the firmware for the microcontroller is located in a Flash memory device (for ease of
debugging and for possible field upgradeability), and all memory and memory-mapped I/O is
located outside the microcontroller, P0 is used as a time-multiplexed low-order address and data
bus. It is not used for general I/O purposes.
8.6.2.2 P1
P1 has two dedicated-function signals, and six implementation-specific control signals, as shown
in Table 8-4: P1 Functions.
Table 8-3: Drive Present Status Byte Format
Bit(s) Name Reset Action R/W Description
1:0 DRVPRES[1:0] N/A RO Drive present sense. 0=drive absent, 1=drive present. Bit 0
corresponds to drive ID 0.