IP-Octal Serial is accessed using 8-bit bytes at odd locations only. It is usually accessed in the I/O space. Shown below in Figures 3 and 4 are the regist4er maps of the IP-Octal Serial. All addresses are offsets from the I/O base address of the IP as set on the IP carrier board.
The SCC2698B Octal UART has four major internal sections, called functional blocks A through D. Each functional block has two serial channels, one timer, and one I/O port.
| Hex | Dec | Binary | Read | Write |
| Functional Block A | ||||
| 1 | 1 | 0000001 | MR1a, MR2a | MR1a, MR2a |
| 3 | 3 | 0000011 | SRa | CSRa |
| 5 | 5 | 0000101 | RESERVED | CRa |
| 7 | 7 | 0000111 | RHRa | THRa |
| 9 | 9 | 0001001 | IPCRA | ACRA |
| B | 11 | 0001011 | ISRA | IMRA |
| D | 13 | 0001101 | CTUA | CTURA |
| F | 15 | 0001111 | CRLB | CTLRB |
| 11 | 17 | 0010001 | MR1b, MR2b | MR1b, MR2b |
| 13 | 19 | 0010011 | SRb | CSRb |
| 15 | 21 | 0010101 | RESERVED | CRb |
| 17 | 23 | 0010111 | RHRb | RHRb |
| 19 | 25 | 0011001 | RESERVED | RESERVED |
| 1B | 27 | 0011011 | INPUT PORT A | OPCRA |
| 1D | 29 | 0011101 | START C/T A | RESERVED |
| 1F | 31 | 0011111 | STOP C/T A | RESERVED |
| Functional Block B | ||||
| 21 | 33 | 0100001 | MR1c, MR2c | MR1C, MR2C |
| 23 | 35 | 0100011 | SRc | CSRc |
| 25 | 37 | 0100101 | RESERVED | CRc |
| 27 | 39 | 0100111 | RHRc | THRc |
| 29 | 41 | 0101001 | IPCRB | ACRB |
| 2B | 43 | 0101011 | ISRB | IMRB |
| 2D | 45 | 0101101 | CTUB | CTURB |
| 2F | 47 | 0101111 | CRLB | CTLRB |
| 31 | 49 | 0110001 | MR1d, MR2d | MR1d, MR2d |
| 33 | 51 | 0110011 | SRd | CSRd |
| 35 | 53 | 0110101 | RESERVED | CRd |
| 37 | 55 | 0110111 | RHRD | THRd |
| 39 | 57 | 0111001 | RESERVED | RESERVED |
| 3B | 59 | 0111011 | INPUT PORT B | OPCRB |
| 3D | 61 | 0111101 | START C/T B | RESERVED |
| 3F | 63 | 0111111 | STOP C/T B | RESERVED |
Figure 3 Register Map of SCC2698, Blocks A and B
| Hex | Dec | Binary | Read | Write |
| Functional Block C | ||||
| 41 | 65 | 1000001 | MR1e, MR2e | MR1e, MR2e |
| 43 | 67 | 1000011 | SRe | CSRe |
| 45 | 69 | 1000101 | RESERVED | CRe |
| 47 | 71 | 1000111 | RHRe | THRe |
| 49 | 73 | 1001001 | IPCRC | ACRC |
| 4B | 75 | 1001011 | ISRC | IMRC |
| 4D | 77 | 1001101 | CTUC | CTURC |
| 4F | 79 | 1001111 | CRLC | CTLRC |
| 51 | 81 | 1010001 | MR1f, MR2f | MR1f, MR2f |
| 53 | 83 | 1010011 | SRf | CSRf |
| 55 | 85 | 1010101 | RESERVED | CRf |
| 57 | 87 | 1010111 | RHRf | THRf |
| 59 | 89 | 1011001 | RESERVED | RESERVED |
| 5B | 91 | 1011011 | INPUT PORT C | OPCRC |
| 5D | 93 | 1011101 | START C/T C | RESERVED |
| 5F | 95 | 1011111 | STOP C/T C | RESERVED |
| Functional Block D | ||||
| 61 | 97 | 1100001 | MR1g, MR2g | MR1g, MR2g |
| 63 | 99 | 1100011 | SRg | CSRg |
| 65 | 101 | 1100101 | RESERVED | CRg |
| 67 | 103 | 1100111 | RHRg | THRg |
| 69 | 105 | 1101001 | IPCRD | ACRD |
| 6B | 107 | 1101011 | ISRD | IMRD |
| 6D | 109 | 1101101 | CTUD | CTURD |
| 6F | 111 | 1101111 | CRLD | CTLRD |
| 71 | 113 | 1110001 | MR1h, MR2h | MR1h, MR2h |
| 73 | 115 | 1110011 | SRh | CSRh |
| 75 | 117 | 1110101 | RESERVED | CRh |
| 77 | 119 | 1110111 | RHRh | RHRh |
| 79 | 121 | 1111001 | RESERVED | RESERVED |
| 7B | 123 | 1111011 | INPUT PORT D | OPCRD |
| 7D | 125 | 1111101 | START C/T D | RESERVED |
| 7F | 127 | 1111111 | STOP C/T D | RESERVED |
Figure 4 Register Map of SCC2698, Blocks C and D
For NuBus applications see the section following, Nubus Addressing.